Process for making a container

ABSTRACT

A transparent multi-layer container comprising a co-extrudate of an oxygen-barrier resin layer and an orienting resin layer which is monoaxially or biaxially oriented is disclosed. An adhesive resin layer is preferably interposed between the oxygen-barrier layer and the orienting resin layer, and this co-extrudate is drawn and molded at a specific temperature determined relatively to the melting points and softening points of the respective resins. This container is excellent in the combination of transparency, rigidity, mechanical strength, gas-barrier property and interlaminar peel strength.

This is a division, of application Ser. No. 821,484 filed Aug. 3, 1977.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a multi-layer plastic drawn and moldedcontainer excellent in transparency, rigidity, mechanical strength,water resistance and gas barrier property to oxygen and the like andhaving a practically satisfactory interlaminar peel strength underfalling, shaking or impact, and to a process for the preparation of thisexcellent container.

(2) Description of the Prior Arts

It is well known that when a thermoplastic resin is drawn at arelatively low temperature, namely at a temperature lower than themelting point or softening point of the resin or a temperature justabove the melting point or softening point of the resin, as a result oforientation of the polymer chain or crystal, such properties asrigidity, mechanical strength, gas barrier property and transparency canbe improved. These improvements are practically utilized in biaxiallydrawn films, filaments, drawn tapes, biaxially drawn blow bottles anddraw-molded cups.

In the field of narrow- and broad-mounted hollow plastic containers, forexample, a biaxially drawn blow bottle of the vinylidene chloride resintype molded according to the method disclosed in Japanese PatentPublication No. 8583/63 has heretofore been broadly used as a ketchupbottle because it has an excellent gas barrier property. However,because of generation of poisonous gases on burning or migration of themonomer or additive into the content, bottles of this type are hardlyused at the present. Biaxially drawn blow bottles of polypropyleneformed according to the principle, method and apparatus disclosed inJapanese Patent Publication No. 16245/63, Japanese Patent ApplicationLaid-Open Specification No. 3492/71, etc., have excellent transparency,rigidity and mechanical strength, and they are broadly used as bottlesfor shampoo or the like instead of polyvinyl chloride bottles in U.S.A.and as bottles for medicines, for example, Ringer's solution, instead ofglass bottles in Japan. Further, broad-mouthed polypropylene cupsprepared by solid-phase pressure forming at a relatively low temperatureaccording to the method disclosed in Kunststoffe Bd. 65, 1975, H. 10,page 666 have now been attracting attentions as substitutes forpolyvinyl chloride cups. Further, biaxially drawn blow bottles ofpolyethylene terephthalate disclosed in the specification of U.S. Pat.No. 3,733,309 have been test-marketed as bottles for carbonated drinksand now attract attentions in the art.

In case of the above-mentioned biaxially drawn blow bottles of thevinylidene chloride resin type, when a contained liquid, semi-liquid orpasty food has contact with the inner wall of the bottom, a problem ofmigration of the monomer or the like rises, and they cannot be regardedas practical semi-rigid containers. Biaxially drawn blow bottles ofpolypropylene and polypropylene cups prepared by solid phase pressureforming are inferior in the gas barrier property, and they cannotsubstantially be applied to foods of which the preservability issensitive to oxygen permeating through the container wall. Althoughbiaxially drawn blow bottles of polyethylene terephthalate have arelatively high gas barrier property and are very excellent in rigidityand transparency, when they are allowed to stand in an atmospheremaintained at 60° to 70° C. for 3 to 5 minutes, they show such thermalshrinkage as an empty volume shrinkage of 1 to 3%, a total heightshrinkage of 0.4 to 0.8% and a barrel diameter shrinkage of 0.7 to 1.2%.Further, when they are allowed to stand in an atmosphere maintained at80° C. for 1 minute, they are deformed to such an extent that theycannot be practically used. Accordingly, these bottles cannot be usedwhen hot filling of contents is conducted or for storage of foodsrequiring heat sterilization, for example, sauces.

For the foregoing reasons, as in case of melt-molded containers,multi-layer structures in which defects of respective resins arecompensated and which can meet practical demands are required in case ofnot only biaxially drawn blow molded containers prepared by forming athermoplastic resin into a bottomed or bottomless parison and conductingthe step of elongating the parison in the axial direction thereof at arelatively low temperature, for example, the melting point of the resinand the step of inflating the parison in a direction rectangular to theaxial direction simultaneously or in this order (namely in sequence) butalso biaxially drawn cups pressure-formed in the solid phase from asheet at a relatively low temperature.

Drawn multi-layer containers are proposed in, for example, thespecification of U.S. Pat. No. 3,733,309 and Japanese Patent ApplicationLaid-Open Specification No. 32164/73, but these known drawn multi-layercontainers are still insufficient from the practical viewpoint withrespect to the interlaminar strength between every two adjacent layers,selection of consituent resin layers and selection of molding conditionssuch as the molding temperature and draw ratio. In addition, use of anunsaturated carboxylic acid-grafted thermoplastic resin as an adhesiveimproving the interlaminar peel strength has been proposed in, forexample, Japanese Patent Application Laid-Open Specification No.67384/76, but in this proposal, no sufficient regard is paid to therelation between the molding conditions such as the molding temperatureand draw ratio and the adhesiveness.

BRIEF SUMMARY OF THE INVENTION

We found that in order to obtain biaxially drawn blow-molded bottles ordraw-molded containers such as solid phase pressure-formed cups, whichhave a high barrier property to gases such as oxygen and are excellentin the combination of transparency, rigidity, mechanical strength andother physical properties, it is necessary to select very strictlyconstituent resin layers and molding conditions such as the moldingtemperature and draw ratio in view of the practical utility andmoldability.

We also found that when a draw-molded container is prepared from amulti-layer structure comprising an oxygen-barrier thermoplastic resinlayer and a layer of an orienting thermoplastic resin other than theoxygen-barrier thermoplastic resin preferably with an adhesive resinlayer interposed between said two resin layers, in order to attain ahigh interlaminar peel strength, it is very important to select therespective resins so that a specific relation is established among themelting or softening points of the resins and to perform draw-molding ata temperature in a specific range.

In accordance with the present invention, there is provided a containerhaving a multi-layer structure, which comprises a plurality ofthermoplastic resins, wherein at least one layer of the container iscomposed of an oxygen-barrier thermoplastic resin having an oxygenpermeability lower than 5.5×10⁻¹² cc.cm/cm².sec.cmHg as measured at 37°C. and at least one of the remaining layers comprises an orientingthermoplastic resin other than the oxygen-barrier thermoplastic resin,said two resins are selected so that the requirement represented by thefollowing formula:

    |T.sub.B -T.sub.O |≦35° C. (1)

wherein T_(B) stands for the melting or softening point (°C.) of saidoxygen-barrier thermoplastic resin and T_(O) stands for the melting orsoftening point (°C.) of said orienting thermoplastic resin, issatisfied, and wherein at least one of two-dimensional orientationcoefficients (l and m) of at least one layer composed of said orientingthermoplastic resin in a smallest-thickness portion of the container isat least 0.05.

In accordance with the present invention, there is also provided acontainer having a multi-layer structure, which comprises at least onelayer composed of an oxygen-barrier thermoplastic resin having an oxygenpermeability lower than 5.5×10⁻¹² cc.cm/cm².sec.cmHg as measured at 37°C., at least one layer comprising an orienting thermoplastic resin otherthan the oxygen-barrier thermoplastic resin and at least one layerinterposed between said oxygen-barrier thermoplastic resin layer andsaid orienting thermoplastic resin layer and being composed of a resinhaving an adhesiveness to both of said resins, wherein said three resinsare selected so that the requirements represented by the followingformulae:

    |T.sub.B -T.sub.O |≦35° C. (1)

and

    90° C.≧T.sub.O -T.sub.C >2° C.        (2)

wherein T_(B) stands for the melting or softening point (°C.) of saidoxygen-barrier thermoplastic resin, T_(O) stands for the melting orsoftening point (°C.) of the melting or softening point of saidorienting thermoplastic resin and T_(C) stands for the melting orsoftening point (°C.) of said adhesive resin, at least one oftwo-dimensional orientation coefficients (l and m) of at least one layercomposed of said orienting thermoplastic resin in a smallest-thicknessportion of the container is at least 0.05, and wherein the layer of saidadhesive resin is substantially nonoriented.

This invention will now be described in detail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Resin Components

In the container of this invention, in order to attain the foregoingobjects, it is important that a gas-barrier resin having an oxygenpermeability lower than 5.5×10⁻¹² cc.cm/cm².sec.cmHg as measured at 37°C. and an orienting thermoplastic resin other than the gas-barrier resinshould be selected and combined as the layer-constituting resin so thatthe difference (Δt=|T_(B) -T_(O) |) between the melting or softeningpoint (T_(B)) of the the gas-barrier resin and the melting or softeningpoint (T_(O)) of the orienting thermoplastic resin is smaller than 35°C., especially smaller than 10° C.

In the instant specification and appended claims, the melting point isdefined as the thermodynamic primary transition point at which thecrystal phase of a crystalline or semi-crystalline polymer is molten, asdescribed in "Crystallization of Polymers" written by Leo Mandelkern andpublished by McGrow-Hill Book Company in 1964, and in general, themelting point can easily be determined according to the differentialthermal analysis method, the specific heat-temperature curve method, thepolarizing microscope method, the X-ray diffractometry method, theinfrared absorption spectrum method or the like.

Further, in the instant specification and appended claims, the softeningpoint corresponds to the thermodynamic secondary transition point, i.e.,the glass transition point, at which a polymer is substantiallysoftened. This softening point is described in, for example, "Physics ofPolymers" compiled by Japanese Association of Physics and published byAsakura Shoten in 1963 and can easily be determined by the specificheat- or specific volume-temperature cruve method, the differentialthermal analysis method or the industrial test methods such as methodsof ASTM D 648-56, ASTM D 1525-58T and ASTM D 569-48.

In general, melt-extrudable thermoplastic resins having a goodgas-barrier property to gases such as oxygen and carbon dioxide gas, forexample, ethylenevinyl alcohol copolymers and nylon resins, containpolar groups such as hydroxyl groups and amide groups on the main orside chains of polymers. The melting or softening points of these resinsvary broadly depending on the content of polar groups, the chemicalcomposition and other factors.

As described in the specifications of U.S. Pat. Nos. 3,183,203 and3,419,654, ethylene-vinyl alcohol copolymers can be obtained bysaponifying a copolymer of ethylene or a combination of the majority ofethylene and the minority of other olefin such as propylene with a vinylester of a lower fatty acid such as vinyl formate, vinyl acetate, vinylpropionate or the like, especially an ethylene-vinyl acetate copolymer.It has been found that in ethylene-vinyl alcohol copolymer resins, thefollowing relation is substantially established between the meltingpoint (Tm) determined according to the differential thermal analysismethod or the like and the mole content (%) of ethylene:

    Tm=1.64X+68                                                (3)

wherein Tm stands for the melting point of an ethylene-vinyl alcoholcopolymer having an ethylene content of 0 to 80 mole % and X stands forthe vinyl alcohol content (mole %) in the copolymer.

It has also been found that in case of nylons of the ring openingpolymerization type the melting point varies depending on the kind ofthe amino acid monomer, in case of nylons of the polycondensation typethe melting point varies depends on the kind of the acid and the amine,in case of nylons of the copolymer type the melting point variesdepending on the monomer composition, and that in case of nylon polymerblends the melting point varies depending on the polymer blending ratio.Melting points of these nylon type polymers as determined according tothe differential thermal analysis method or the like are as shown inTable 1 given hereinafter.

                                      Table 1                                     __________________________________________________________________________    Melting Points of Polyamide Resins                                            Resin                  Melting Point (Tm), °C.                         __________________________________________________________________________    Polyamides of Ring Opening Polymerization Type                                ω-Aminocaproic acid polymer (nylon 6)                                                          223                                                    ω-Aminoheptanoic acid polymer (nylon 7)                                                        233                                                    ω-Aminocaprylic acid polymer (polymer 8)                                                       200                                                    ω-Aminopelargonic acid polymer (nylon 9)                                                       210                                                    ω-Aminodecanoic acid polymer (nylon 10)                                                        188                                                    ω-Aminoundecanoic acid polymer (nylon 11)                                                      185                                                    ω-Aminododecanoic acid polymer (nylon 12)                                                      180                                                    ω-Aminotridecanoic acid polymer (nylon 13)                                                     180                                                    Polyamides of Polycondensation Type                                           Polyhexamethylene adipamide (6,6-nylon)                                                              265                                                    Polyhexamethylene azelamide (6,9-nylon)                                                              185                                                    Polyhexamethylene sebacamide (6,1-nylon)                                                             225                                                    Polyhexamethylene dodecamide (6,12-nylon)                                                            212                                                    Polyhexamethylene tridecamide (6,13-nylon)                                                           204                                                    Polydecamethylene hexamide (10,6-nylon)                                                              225                                                    Polydecamethylene sebacamide (10,10-nylon)                                                           213                                                    Polydecamethylene dodecamide (10,12-nylon)                                                           195                                                    Polydecamethylene tridecamide (10,13-nylon)                                                          187                                                    Polydodecamethylene adpiamide (12,6-nylon)                                                           210                                                    Polydodecamethylene sebacamide (12,10-nylon)                                                         190                                                    Polydodecamethylene dodecamide (12,12-nylon)                                                         185                                                    Polytridecametylene sebacamide (13,10-nylon)                                                         170                                                    Polytridecamethylene tridecamide (13,13-nylon)                                                       174                                                    Nylons of Copolymer Type                                                      6,6-Nylon-6,10-Nylon Copolymers                                               6,6-nylon content of 0 mole %                                                                        225                                                    6,6-nylon content of 20 mole %                                                                       202                                                    6,6-nylon content of 30 mole %                                                                       192                                                    6,6-nylon content of 40 mole %                                                                       195                                                    6,6-nylon content of 60 mole %                                                                       210                                                    6,6-nylon content of 80 mole %                                                                       233                                                    6,6-nylon content of 100 mole %                                                                      265                                                    6-Nylon-6,6-Nylon Copolymers                                                  6,6-nylon content of 0 mole %                                                                        223                                                    6,6-nylon content of 20 mole %                                                                       163                                                    6,6-nylon content of 40 mole %                                                                       156                                                    6,6-nylon content of 60 mole %                                                                       170                                                    6,6-nylon content of 80 mole %                                                                       220                                                    6,6-nylon content of 100 mole %                                                                      265                                                    Nylon Polymer Blends                                                          6-Nylon-6,6-Nylon Blends                                                      6,6-nylon mixing ratio of 0 %                                                                        223                                                    6,6-nylon mixing ratio of 20 mole %                                                                  215                                                    6,6-nylon mixing ratio of 40 mole %                                                                  230                                                    6,6-nylon mixing ratio of 60 mole %                                                                  248                                                    6,6-nylon mixing ratio of 80 mole %                                                                  250                                                    6,6-nylon mixing ratio of 100 mole %                                                                 265                                                    __________________________________________________________________________

As pointed out hereinbefore, in resins having a bsrrier property to agas such as oxygen, for example, ethylene-vinyl alcohol copolymers andnylon resins, the melting or softening point varies depending on thecontent of a polar group such as a hydroxyl or amide group or thechemical composition.

Data of the oxygen permeability (PO₂, cc.cm/cm².sec.cmHg) as determinedat 37° C. in the absolute dry state of ethylene-vinyl alcohol copolymersand polyamides excellent in the barrier property to gases such as oxygenare shown in Table 2 given hereinafter.

                  Table 2                                                         ______________________________________                                        oxygen Permeabilities of High Gas-Barrier Resins                                                  PO.sub.2 ×10.sup.12 cc.cm/                                              cm.sup.2.sec.cmHg                                         Resin               (at 37° C. and 0 % RH)                             ______________________________________                                        Ethylene-Vinyl Alcohol Copolymers                                             Vinyl alcohol content of 40 mole %                                                                3.8                                                       Vinyl alcohol content of 50 mole %                                                                0.5                                                       Vinyl alcohol content of 60 mole %                                                                0.1                                                       Vinyl alcohol content of 70 mole %                                                                0.07                                                      Vinyl alcohol content of 80 mole %                                                                0.06                                                      Polyamides                                                                    6-Nylon             4.0                                                       8-Nylon             4.5                                                       11-Nylon            4.9                                                       12-Nylon            5.3                                                       6,6-Nylon           0.69                                                      6,10-Nylon          0.8                                                       10,6-Nylon          0.81                                                      6-Nylon-6,6-nylon copolymer                                                   (6-nylon content = 10 mole %)                                                                     1.0                                                       6-Nylon-6,6-nylon copolymer                                                   (6-nylon content = 30 mole %)                                                                     2.0                                                       ______________________________________                                    

In this invention, use of a thermoplastic resin having an oxygenpermeability (PO₂) lower than 4.5×10⁻¹² cc.cm/cm².sec.cmHg as determinedat 37° C. is preferred, and an ethylene-vinyl alcohol copolymer,especially a saponified ethylene-vinyl acetate copolymer having anethylene content of 25 to 65 mole % and a degree of saponification of atleast 99 mole %, is most preferred. Of course, nylon resins can also beused conveniently. These oxygen-barrier thermoplastic resins should, ofcourse, have a molecular weight sufficient to form a film.

In this invention, in order to obtain a container comprising anoxygen-barrier resin layer (A) and an orienting resin layer (B), inwhich the orienting resin layer is effectively oriented and theadhesiveness between the two resin layers and the transparency as awhole are excellent, the two resins should be selected so that theirmelting or softening points satisfy the requirement represented by theabove formula (1).

In general, when a parison or sheet having a multilayer structure issubjected to draw molding or solid phase pressure forming, theinterlaminar peel strength between two layers is drastically reduced. Itis believed that the reason for reduction of the interlaminar peelstrength is that the respective layers show different responsesdeformation caused from the outside and a force given from the outside,namely they differ from each other in viscoelastic characteristics,unless the layer-constituting resins are thermoplastic resins havingquite the same chemical and physical properties and therefore, differentstresses or strains are caused in interfaces between every two adjacentlayers, resulting in reduction of the adhesive force. This undesirablephenomenon is often observed also in the case where an unsaturatedcarboxylic acid-modified thermoplastic resin is used as an adhesivelayer between a layer of a versatile resin such as polyolefin and alayer of a high gas-barrier resin such as mentioned above.

We found that when a parison or sheet having a multi-layer structure ismolded into a container, in order to enhance the transparency andinterlaminar peel strength, it is important that a high oxygen-barrierresin such as mentioned above and an orienting resin such as mentionedabove should be selected so that the difference (Δt) between the meltingor softening point (T_(B)) of the high oxygen-barrier resin and themelting or softening point (T_(O)) of the orienting resin is not largerthan 35° C., and that at least one of two-dimensional orientationcoefficients (l and m) of at least one layer of the orienting resin in asmallest-thickness portion of the final molded container should be atleast 0.05.

More specifically, it was found that when the melting or softening point(T_(B)) of the high barrier resin is lower than the melting or softeningpoint (T_(O)) of the orienting resin by more than 35° C., undercontainer-molding conditions giving the above-mentioned degree oforientation, the high barrier resin is in the completely molten stateand because of extreme thickness unevenness of the high barrier resinlayer caused in response to the temperature distribution of the parisonor sheet at the molding step or of heat generation caused bysolidification or crystallization of the high barrier resin at thecooling stage after the molding step, the orientation and transparencyof the orienting resin layer other than the high barrier resin layer aredrastically reduced. Moreover, it was found that when the melting orsoftening point (T_(B)) of the high barrier resin is higher than themelting or softening point (T_(O)) of the orienting resin by more than35° C., under molding conditions giving the above-mentioned degree oforientation, the high barrier resin is in the relativelyviscoelastically solid state and a high stress is generated on theinterface between the high barrier resin layer and the adjacent otherresin layer, to cause drastic reduction of the interlaminar peelstrength in the final molded container. As will be apparent from thesefindings, it is especially important that the high oxygen-barrier resinand orienting resin should be selected so that the difference (Δt)between the melting or softening point (T_(B)) of the highoxygen-barrier resin and the melting or softening point (T_(O)) of theorienting resin is not larger than 35° C.

As the orienting thermoplastic resin (B), any of known thermoplasticresins capable of being oriented by drawing, other than theabove-mentioned oxygen-barrier thermoplastic resin (A), can be used inthis invention, so far as the above-mentioned requirements aresatisfied. For example, homopolymers of olefins represented by thefollowing formula: ##STR1## wherein R stands for a hydrogen atom or analkyl group having up to 4 carbon atoms, such as ethylene, propylene,butene-1, pentene-1 and 4-methylpentene-1, copolymers of these olefins,copolymers of these olefins with a small amount, generally 0.05 to 10%by weight based on the olefin, of other ethylenically unsaturatedmonomer such as vinyl acetate, an acrylic acid ester or the like, andblends of two or more of the foregoing polymers can be preferablyemployed for production of multi-layer parisons or sheets to be used inthis invention, so far as they are crystalline. In order to obtain amolded container excellent in the rigidity and mechanical strength bydraw molding, it is very important that homopolymers or copolymers ofolefins should be crystalline. As the olefin homopolymer or copolymer,crystalline polypropylene is most preferred in view of the transparencyand mechanical properties. In addition, there can be mentioned anethylenepropylene copolymer, high density polyethylene,poly-4-methylpentene-1, polybutene-1 and medium density polyethylene inan order of importance. As the ethylenepropylene copolymer, acrystalline polymer comprising 0.5 to 15 mole % of ethylene and 85 to95.5 mole % of propylene is especially valuable. In general, the olefinhomopolymer or copolymer to be used should have a molecular weightsufficient to form a film, and it is preferred that the melt index (asdetermined according to the method of ASTM D-1238) of the olefinhomopolymer or copolymer be 0.0001 to 5, especially 0.01 to 2.5.

Another instances of the orienting thermoplastic resin includepolycarbonates and thermoplastic acrylic resins. As preferred examplesof the polycarbonate, there can be mentioned polymers of carbonic acidesters obtained by reaction of bisphenol with phosgene, and as preferredexamples of the acrylic resin, there can be mentioned homopolymers andcopolymers of acrylic acid esters and methacrylic acid esters.

In this invention, the orienting resin layer may be a layer of a blendof the orienting thermoplastic resin with other thermoplastic resin, forexample, the above-mentioned oxygen-barrier resin or an adhesive resindescribed hereinafter, so far as the orienting thermoplastic resin is amain component. If this feature is adopted, flashes formed at the stepof molding of containers can be used for formation of the orientingresin layers.

In this invention, it is preferred that the oxygen-barrier thermoplasticresin (A) and the orienting thermoplastic resin (B) be selected andcombined so that the requirement represented by the following formula:

    0.61T.sub.O -56.8≦X≦0.61T.sub.O -26.2        (5)

wherein T_(O) stands for the melting or softening point (°C.) of theorienting thermoplastic resin (B) and X stands for the content (mole %)of the vinyl alcohol units in the oxygen-barrier thermoplastic resin(A), is satisified.

In this invention, in general, it is preferred that an adhesive resin(C) having an adhesiveness to both the oxygen-barrier thermoplasticresin layer (A) and the orienting thermoplastic resin layer (B) beinterposed between the two layers (A) and (B).

Any of known resins having an adhesiveness to the above-mentionedoxygen-barrier thermoplastic resin (A) and orienting thermoplastic resin(B) can be used as the adhesive resin (C). In general, however, as theadhesive polymer (C), there are employed thermoplastic polymers havingcarbonyl groups ##STR2## derived from functional groups of freecarboxylic acids, carboxylic acid salts, carboxylic acid esters,carboxylic acid amides, carboxylic anhydrides, carbonic acid esters,urethane, urea or the like. In these thermoplastic polymers, thecarbonyl group concentration may be changed in a broad range, but ingeneral, it is preferred to use a thermoplastic polymer containingcarbonyl groups at a concentration of 10 to 1400 millimoles per 100 g ofthe polymer, especially 30 to 1200 millimoles per 100 g of the polymer.Preferred adhesive resins include polyolefins modified with at least oneethylenically unsaturated monomer selected from unsaturated carboxylicacids and anhydrides, esters and amides thereof, especiallypolypropylene, high density polyethylene, low density polyethylene andethylene-vinyl acetate copolymers modified with at least one memberselected from acrylic acid, methacrylic acid, crotonic acid, fumaricacid, itaconic acid, maleic anhydride, itaconic anhydride, citraconicanhydride, ethyl acrylate, methyl methacrylate, ethyl maleate,2-ethylhexyl acrylate, acrylamide, methacrylamide, coconut fatty acidamide and maleimide. In addition, as the adhesive resin, there can beused ethylene-acrylate copolymers, ionomers (such as Surlyn®manufactured by Du Pont), polyalkylene oxide-polyester block copolymers,carboxylmethyl cellulose derivatives, and blends of these polymers withpolyolefins.

In order to draw a parison or sheet having a multi-layer structure underthe above-mentioned conditions, the melting or softening point of theadhesive resin is limited.

More specifically, the melting or softening point (T_(C), °C.) of theadhesive resin (C) should be lower than the melting or softening point(T_(O), °C.) of the orienting thermoplastic resin (B), and in view ofthe interlaminar peel strength and moldability of a multilayer parisonor sheet to be drawn, it is preferred that the requirement representedby the following formula:

    90° C.=T.sub.O -T.sub.C =2° C.               (2)

wherein T_(O) stands for the melting or softening point (°C.) of theorienting thermoplastic resin (B) and T_(C) stands for the melting orsoftening point (°C.) of the adhesive resin (C), be satisfied.

MULTI-LAYER STRUCTURE

The layer structure of the multi-layer container is preferably decidedaccording to the use and physical properties of the container. Forexample, when the content is a non-aqueous content, a layer of achemically inactive resin such as a polyolefin need not be used as theinnermost layer, but when the content is a food or drink, it ispreferred to use a polyolefin considered to be safest from the sanitaryviewpoint as the innermost layer. Layer structures including anoxygen-barrier thermoplastic resin layer (designated as "A") and anorienting thermoplastic resin layer (designated as "B" or "B'")optionally with an adhesive resin layer (designated as "C"), which arepreferably used in this invention, are as follows:

    ______________________________________                                         (i)   Two-Layer Structure:                                                          B/A                     (i)                                            (ii)   Three-Layer Structure:                                                        B/C/A                   (ii-1)                                                B/A/B                   (ii-2)                                                B/A/B'                  (ii-3)                                         (iii)  Four-Layer Structure:                                                         B/B'/C/A                (iii-1)                                               B/C/A/C                 (iii-2)                                               B/C/A/B'                (iii-3)                                        (iv)   Five-Layer Structure:                                                         B/C/A/B                 (iv-1)                                                B/C/A/C/B'              (iv-2)                                                (B+A+C)/C/A/C/(B+A+C)   (iv-3)                                         (v)    Six-Layer Structure:                                                          B/B'/C/A/C/B            (v-1)                                                 B/(B+A+C)/C/A/C/B       (v-2)                                          (vi)   Seven-Layer Structure:                                                        B/(B+A+C)/C/A/C/(B+A+C)/B                                                                             (vi-1)                                                B/B/'/C/A/C/B'/B        (vi-2)                                         ______________________________________                                    

Among these multi-layer structures, five-layer structures (iv-1), (iv-2)and (iv-3) and seven-layer structure (vi-1) are especially preferred.

It is preferred that in the above-mentioned multilayer structure, 0.2 to50%, especially 2 to 20%, of the total thickness of the final containerbe occupied by the oxygen-barrier resin layer (A).

Further, it is preferred that the respective resin layers be present inthe multi-layer structure at the following thickness ratios:

B:A=from 1:1 to 500:1 and

B:C=from 1:1 to 500:1

CONTAINER

In the intended multi-layer draw-molded container or multi-layer solidphase pressure-formed container of the present invention, all the layersconstituting the container should not necessarily be draw-molded orsolid phase pressure-formed. In this invention, a resin layer in which arelatively excellent transparency cannot be obtained according to theconventional melt-molding method is draw-molded or solid phasepressure-formed. In this invention, it is important to selectlayer-constituting resins so that at least one of two-dimensionalorientation coefficients (l and m) of at least one layer of the finalcontainer is at least 0.05.

The two-dimensional orientation coefficients referred to in the instantspecification and appended claims can be determined according to themethod described in "Polymers, vol. 15, No. 175, page 868" written byYasunori Nishijima and published by Japanese Association of Polymers in1966, in which by utilizing optically antisotropic characteristics of afluorescent molecule, the degree and mode of molecular orientation of apolymer, i.e., a thermoplastic resin, caused by solid deformation or byflowing in the solution or melt state are qualitatively andquantitatively determined. When the two-dimensional orientation in thewall face of the container of this invention is considered in the lightof teachings of the above literature reference, the two-dimensionalorientation degrees can be quantitatively represented as follows:

    II (ω)=Kφ(l·cos.sup.4 ω+m·sin.sup.4 ω+3/8 n)                                            (6)

wherein I (ω) stands for the intensity of the polarized component of thefluorescence emitted from a thermoplastic resin as the sample, indicatesthat the vibration direction of incident polarized light is in parallelto the direction of measured polarized light, ω stands for the rotationangle of the sample with respect to the vibration direction of saidpolarized light, K designates a maximum excitation probability when themolecular axis of the sample is in parallel to the vibration directionof excited fluorescent light, φ stands for the molecular fluorescentcontraction, l designates the ratio of orientation of the molecule inone optional direction in the wall face of the container, m designatesthe ratio of orientation in a direction rectangular to the orientationdirection of l, n stands for the ratio of non-orientation in the wallface, and the sum of l, m and n is 1 (l+m+n=1).

When the adhesive resin (C) is interposed between the oxygen-barrierresin layer (A) and the orienting resin layer (B), it is preferred thatthe adhesive resin layer (C) be substantially non-oriented.

In accordance with another preferred embodiment of this invention, thereis provded a multi-layer container wherein the oxygen-barrier resin andthe orienting resin are selected so that the requirement represented bythe following formula:

    |T.sub.B -T.sub.O |≦10° C. (7)

wherein T_(B) and T_(O) are as defined above, is satisfied, at least oneof two-dimensional orientation coefficients (l and m) of at least onelayer of the orienting thermoplastic resin in a smallest-thicknessportion of the container is at least 0.1, each resin layer has a haze(Hz) lower than 10%, and wherein the bonding strength between every twoadjacent layer is at least 20 g/cm.

In order to obtain a container having much preferred transparency andrigidity, it is important that the difference Δt should be not largerthan 10° C. and at least one of two-dimensional orientation coefficients(l and m) should be at least 0.1. When at least one of thetwo-dimensional orientation coefficients of the orienting resin layer isat least 0.1, namely when the orienting resin layer is drawn at arelatively high draw ratio, there is observed a tendency that thebonding strength between adjacent layers is reduced, as pointed outhereinbefore. However, we found that if each layer constituting thecontainer has a haze (Hz) lower than 10%, namely if each layer isexcellent in the transparency, the peeling is not visually noted undershaking or falling between two adjacent layers, and that this effect canbe prominently attained if the interlaminar bonding strength betweenevery two adjacent layers is at least 20 g/cm.

The molded container of this invention has a unit volume (the volume perunit weight, g, of the resin) of 0.01 to 5 dl/g, especially 0.05 to 2dl/g, though the unit volume is changed to some extent depending on theintended use of the container. The wall thickness of the container ofthis invention is adjusted in a range of from 0.02 to 1 mm, especiallyfrom 0.08 to 0.8 mm. When the unit volume and wall thickness areappropriately chosen within these ranges, a preferred combination ofhigh interlaminar peel strength, high gas-barrier property, highrigidity and high transparency can be attained.

PREPARATION PROCESS

The container of this invention can be prepared according to a processcomprising forming a parison or sheet having the above-mentionedmulti-layer structure by co-melt-extrusion, and molding the parison orsheet into a container at a molding temperature (Tm) satisfying therequirement represented by the following formula:

    |Tm-T.sub.B |≦30° C.       (8)

wherein T_(B) is as defined above and Tm stands for the moldingtemperature (°C.), and under such conditions that orientation of theorienting thermoplastic resin is caused at least in a smallest-thicknessportion of the container.

A parison or sheet having the above-mentioned multi-layer structure canbe formed by known molding means. For example, a multi-layer parison canbe prepared by concurrent extrusion or injection molding of theabove-mentioned resins in a layer structure as mentioned hereinbefore.Further, a multi-layer sheet can be prepared by extruding theabove-mentioned resins in a multi-layer structure as mentionedhereinbefore according to known means and molding the extrudate into asheet according to the known T-die molding method. The so obtainedlaminate sheet may be subjected to a post treatment such as rolling.

The importance that the temperature (Tm) for molding the multi-layerparison or sheet under drawing should be in the range satisfying therequirement represented by the formula (8) will be apparent from theillustration given hereinbefore with respect to the resin components.

When the adhesive resin layer (C) is interposed between theoxygen-barrier thermoplastic resin layer (A) and the orienting resinlayer (B), it also is important that the multi-layer parison or sheetshould be monoaxially or biaxially draw-molded at a temperature (Tm)higher than the melting or softening point (T_(C)) of the adhesive resin(C) but lower than the melting or softening point (T_(O)) of theorienting thermoplastic resin (B).

When monoaxial or biaxial draw-molding is carried out at a temperature(Tm) satisfying the requirement represented by the following formula:

    T.sub.O >Tm≧T.sub.C                                 ( 9)

according to a preferred embodiment of this invention, drawing iseffected while the orienting thermoplastic resin (B) is in thenon-softened state and the adhesive resin (C) is in the molten orsoftened state, and while effective orientation can be given to theorienting thermoplastic resin, the interlaminar peel strength betweenthe orienting thermoplastic resin layer (B) and the oxygen-barrierthermoplastic resin layer (A) can be remarkably enhanced. Whendraw-molding is carried out at a temperature lower than the melting orsoftening point of the adhesive resin (C), as shown in Example 7 givenhereinafter (see comparative bottle BB), in the resulting draw-moldedbottle, delamination is readily caused between the oxygen-barrier resinlayer (A) and the orienting resin layer (B) under falling shock or thelike. On the other hand, as shown in Example 7 given hereinafter, whendraw-molding is carried out at a temperature higher than the melting orsoftening point of the orienting resin (B), a heated parison (parisonwill be often referred to as "pipe" hereinafter) is poor in theform-retaining property and it is readily deformed, and it sometimebecome impossible to perform draw-molding. If draw-molding be possible,the resulting bottle is insufficient in such properties as transparencyand smoothness.

In contrast, when the multi-layer parison or sheet is draw-molded at atemperature (Tm) higher than the melting or softening point of theadhesive resin but lower than the melting or softening point of theorienting resin according to this invention, as shown in Examples givenhereinafter, a draw-molded container excellent in such properties asrigidity, mechanical strength, transparency and smoothness can beobtained with good moldability and processability. Moreover, theinterlaminar peel strength between the oxygen-barrier resin layer (A)and the orienting resin layer (B) can be enhanced to a level exceeding135 g/cm of the width, and in the resulting container, delamination isnot substantially caused under falling shock.

The reason why the interlaminar strength of the container can beprominently improved by conducting draw-molding under theabove-mentioned temperature condition according to the presentembodiment of this invention has not been completely elucidated, but itis construed that main causes are as follows.

The adhesive resin (C) in the molten or softened state at thedraw-molding step has an action of moderating stress or strain generatedon the interface between the two resin layers at the draw-molding step,and the interposed adhesive resin (C) present in the molten or softenedstate promotes drawing of the orienting resin layer (B) or theoxygen-barrier resin layer (A).

Under the above-mentioned draw-molding temperature condition of thisembodiment the oxygen-barrier resin layer (A) may be in the molten orsoftened state or in the non-molten or non-solidified state: Forexample, when the oxygen-barrier resin (A) is an ethylenevinyl alcoholcopolymer, it is preferred that monoaxial or biaxial drawing be carriedout while the copolymer is in the molten or softened state. In case ofmonoaxial drawing, the copolymer may be kept in the non-molten orsemi-molten state. On the other hand, when the oxygen-barrier resin (A)is a polyamide resin, in general, there is not such condition.

A hot air circulating passage, an infrared heater, an induction heater,a microwave irradiator, a heater for contact with a heating medium suchas steam or heated oil or a combination of these heating means can beused for maintaining the multi-layer parison or sheet at theabove-mentioned draw-molding temperature (Tm). Of course, it is possibleto perform draw-molding when the temperature of an as-molded parison orsheet having the above-mentioned molded structure is lowered to theabove-mentioned draw-molding temperature.

In this invention, in view of such properties as rigidity, mechanicalstrength and transparency of the resulting container, it is preferredthat the multi-layer parison or sheet be drawn to such as extent that atleast one of two-dimensional orientation coefficients (l and m) of atleast one layer of the orienting resin in a smallest-thickness portionof the container is at least 0.05.

For attaining this feature, in general, it is preferred that the drawratio of the multi-layer parison or sheet be 1.1 to 20, especially 1.5to 5. The drawing speed at the step of forming the multi-layer parisonor sheet into a container differs depending on the kind of the resin,and the drawing speed is appropriately decided within a range causingthe abovementioned drawing effect. It is especially preferred that thedrawing speed be in a range of from 10%/mm to 6,000,000 %/mm.

In this invention, draw-molding of the multilayer parison or sheet intoa container can be performed under the same conditions as known moldingconditions except that the molding temperature (Tm) is maintained withinthe above-mentioned range and drawing is carried out to such an extentthat at least one of two-dimensional orientation coefficients (l and m)is at least 0.05, especially at least 0.1.

For example, formation of a bottle from the multi-layer parison can beaccomplished by drawing of the parison in the axial direction by holdingmeans or a mandrel and drawing of the parison in the lateral directionby blow-in of a fluid. Steps of drawing the parison in the axialdirection and in the lateral direction may be conducted concurrently orin sequence.

Formation of a container such as a cup from the multi-layer sheet can beaccomplished by plug-assist forming (vacuum molding), air-pressureforming, sheet blow molding, draw forming, draw-ironing molding,compression molding, forward extrusion, backward extrusion,forward-backward extrusion and explosion forming. In the instantspecification, these forming methods are collectively called "drawforming method".

When draw-molding is carried out under the abovementioned conditionsaccording to this invention, a container excellent in transparency,rigidity and gas-barrier property and having especially highinterlaminar peel strength can be obtained. Further, by virtue of thedrawing effect, it is made possible to reduce the wall thickness of thecontainer, decrease the weight of the container and reduce amounts usedof resins drastically.

USES

The container of this invention has a desirable combination ofgas-barrier property, rigidity, transparency and interlaminar peelstrength, and they can be valuably applied to various uses.

Because of these advantages, the container of the present invention isvery useful for preserving, without substantial deterioration orquantity loss, various liquid and pasty foods and drinks, for example,bubbling alcoholic drinks such as beer, other alcoholic drinks such asJapanese sake, whisky, distilled spirits, wines, gin fizz and othercocktails, carbonated drinks such as cola, cider and plain soda, fruitdrinks such as straight fruit juices, e.g., lemon juice, orange juice,plum juice, grape juice and strawberry juice and processed fruit juices,e.g., Nector®, vegetable juices such as tomato juice, synthetic drinksand vitamin-incorporated drinks formed by blending a saccharide such assugar or fructose, citric acid, a colorant and a perfume optionally withvitamins, lactic acid beverages, stews, e.g., pre-cooked curry,pre-cooked hash, borsch and beef stew, gravy, e.g., meat sauce, boiledvegetables, fishes and meats, e.g., vinegared pork, sukiyaki, Chinesefood paste of beef and vegetables, Chinese hotchpotch, boiled spinach,boiled mushroom, boiled asparagus, boiled beans, boiled corn andcream-boiled tuna, soups, e.g., consome soup, potage soup, miso soup,pork-incorporated miso soup and vegetable soup cooked with oil, ricefoods, e.g., boiled rice, rice boiled with red beans, toasted boiledrice, frizzled boiled rice, pilaff and rice-gruel, noodles, e.g.,spaghetti, buck-wheat vermicelli, wheat vermicelli, Chinese noodle andItalian noodle, compound condiments, e.g., those for toasted boiled riceor Chinese noodle soup, luxury foods, e.g., tasted boiled red beans,thick and thick bean-meal soups with sugar, sugared and boiled beanswith rice cake or fruits and jelly, boiled beans with treacle poured on,custard pudding, jelly cakes and soft adzuki-bean jelly, processed fishand meat products, e.g., meat dumpling, hamburger, corn beef, ham,sausage, roast fish, smoked fish, bacon and boiled fish paste, fruitproducts, e.g., processed orange, peach, pine-apple, cherry and apple,condiments such as soy, sauce, vinegar, sweet sake, dressing,mayonnaise, ketchup, soybean paste, lard and edible oil, and foods suchas bean curd, jam, butter and margarine; liquid medicines, liquidagricultural chemicals, liquid cosmetics and detergents; ketones such asacetone and methylethyl ketone; aliphatic hydrocarbons such as n-hexaneand n-heptane; alicyclic hydrocarbons such as cyclohexane; aromatichydrocarbons such as benzene, toluene and xylene; chlorine-containingcarbon tetrachloride, tetrachloroethane and tetrachloroethylene; liquidfuels and oils such as gasoline, kerosine, petroleum bendine, fuel oil,thinner, grease, silicone oil, light oil and machine oil; and liquefiedFreon (the trademark of a product manufactured by Du Pont).

This invention will now be described by reference to the followingExamples that by no means limit the scope of the invention.

EXAMPLE 1

Parisons having both the ends opened and having an inner diameter of 10mm, a length of 185 mm and a thickness of 7.5 mm and parisons havingboth the ends opened and having an inner diameter of 15 mm, a length of100 mm and a thickness of 4.5 mm were prepared from the following 24combinations of innermost and outermost layers, intermediate layers andadhesive layers by using an extruder for forming innermost and outermostlayers, which included a full-flighted screw having a diameter of 65 mmand an effective length of 1430 mm and was provided with a melt channeldivided into two flow passages, an extruder for forming adhesive layers,which included a full-flighted screw having a diameter of 40 mm and aneffective length of 880 mm and was provided with a melt channel dividedinto two flow passages, an extruder for forming intermediate layers,which included a full-flighted screw having a diameter of 40 mm and aneffective length of 880 mm, a 5-ply die, a pipe former and a pipecutter.

Resins used for formation of intermediate layers are as follows:

EV1:

Ethylene-vinyl alcohol copolymer having an ethylene content of 45 mole%, a vinyl alcohol content of 55 mole %, a melting point of 154° C. asmeasured according to the differential thermal analysis method(hereinafter referred to as "DTA method") in which thetemperature-elevating rate was 10° C./mm, and an oxygen permeability(PO₂) of 0.23×10⁻¹² cc.cm/cm². sec.cmHg as measured at a temperature of37° C. and a relative humidity of 0%.

EV2:

Ethylene-vinyl alcohol copolymer having an ethylene content of 30 mole%, a vinyl alcohol content of 70 mole %, a melting point of 181° C. asmeasured according to the above-mentioned DTA method and an oxygenpermeability of 0.07×10⁻¹² cc.cm/cm².sec.cmHg as measured under theabove-mentioned conditions.

EV3:

Ethylene-vinyl alcohol copolymer having an ethylene content of 19 mole%, a vinyl alcohol content of 81 mole %, a melting point of 197° C. asmeasured according to the above-mentioned DTA method and an oxygenpermeability of 0.059×10⁻¹² cc.cm/cm².sec.cmHg as measured under theabove-mentioned conditions.

EV4:

Ethylene-vinyl alcohol copolymer having an ethylene content of 66 mole%, a vinyl alcohol content of 34 mole %, a melting point of 120° C. asmeasured according to the above-mentioned DTA method and an oxygenpermeability of 5.4×10⁻¹² cc.cm/cm².sec.cmHg as measured under theabove-mentioned conditions.

Resins used for formation of innermost and outermost layers are asfollows:

PP1:

Isotactic polypropylene having a density of 0.909 g/cc and a meltingpoint of 159° C. as measured according to the above-mentioned DTAmethod.

PP2:

Ethylene-propylene random copolymer having a density of 0.90 g/cc, amelting point of 154° C. as measured according to the above-mentionedDTA method and an ethylene content of 10 mole %.

Resins used for formation of adhesive layers are as follows:

AH1:

Unsaturated carboxylic acid-modified polypropylene having a density of0.90 g/cc and a melting point of 159° C. as measured according to theabove-mentioned DTA method.

AH2:

Unsaturated carboxylic acid-modified polypropylene having a density of0.90 g/cc and a melting point of 154° C. as measured according to theabove-mentioned DTA method.

AH3:

Resin blend having a density of 0.90 g/cc and being composed ofunsaturated carboxylic acid-modified polyethylene having a melting pointof 105° C. as measured according to the above-mentioned DTA method andan unsaturated carboxylic acid-modified polypropylene having a meltingpoint of 155° C. as measured according to the above-mentioned DTAmethod.

These pipes (parisons) were heated for about 30 minutes in a hotair-circulated oven maintained precisely at an atmosphere temperature of155° C. Then, pipes having an inner diameter of 10 mm, a length of 185mm and a thickness of 4.5 mm were formed into bottles having a thicknessof 0.6 mm, an inner capacity of 300 cc and a weight of 22 to 24 g/bottleaccording to the sequent biaxial draw-blowing method at a draw ratio of3 in the longitudinal direction (the bottle height direction) and at adraw ratio of 3.5 in the lateral direction (the bottle circumferencedirection). Bottles having the same dimensions as described above wereprepared from pipes having an inner diameter of 15 mm, a length of 100mm and a thickness of 4.5 mm according to the same sequent biaxialdraw-blowing method at a draw ratio of 1.5 in the longitudinal directionand at a draw ratio of 1.5 in the lateral direction.

For comparison, cylindrical multi-layer bottles having the samedimensions as described above were prepared from some of 24 combinationsaccording to the known direct blow-molding method (blow-molding ofmolten parisons) in which multi-layer parisons as-extruded from the5-ply die and in the molten state were immediately blow-molded.

In each case, the molding was carried out carefully so that thethickness ratio of innermost or outermost layer/adhesivelayer/intermediate layer was as close to 100:1:3 as possible.

With respect to each of the so prepared 58 kinds of bottles, the oxygentransmission rate (QO₂), the haze (Hz) and the orientation coefficients(l, m and n) of the innermost and outermost layers were determinedaccording to the method disclosed in Japanese Patent ApplicationLaid-Open Specification No. 49379/75, the measuring method of JIS K-6714and the above-mentioned fluorescence method, respectively. Further, withrespect to each kind of bottles, 10 sample bottles were chosen and 340 gof an aqueous solution of table salt was filled in each bottle. Then,the filled bottles were allowed to stand in an atmosphere maintained at-1° C. over 3 days and nights, and immediately, they were let to fall ona concrete floor from a height of 1.2 m in an atmosphere maintained at20° C. so that bottle bottoms were caused to hit on the concrete floor.Then, the falling strength represented by the following formula:

    F.sub.B =100×[10-F.sub.1 ]/10

wherein F₁ stands for the number of bottles broken at the first fallingtest and F_(B) denotes the falling strength, was determined. Further,occurrence of delamination was visually examined by a panel of 5 men(the occurrence of delamination was evaluated based on an average valueof the number N of bottles where delamination took at the first fallingtest). From each bottle, specimens having a width of 10 mm and a lengthof 50 mm were cut off in both the vertical direction and circumferentialdirection of the bottle wall, and the peel strength (AT) was measured ata peeling rate of 100 mm/min in an atmosphere maintained at atemperature of 20° C. and a relative humidity of 60%. Results of thesetests are shown in Table 3.

In Table 3, symbols of bottles are expressed by numbers of four figures.The thousands digit indicates the material of the intermediate layer.For example, "1", "2", "3" and "4" indicate EV1, EV2, EV3 and EV4,respectively. Similarly, the hundreds digit indicates the material ofthe adhesive layer and the tens digit indicates the material of theoutermost and innermost layers, and the expression manner is the same asin case of the intermediate layer. The units digits indicate kinds ofbottles. More specifically, "1", "2" and "3" represent a draw-blowmolded bottle drawn at a draw ratio of 1.5 in the longitudinal directionand at a draw ratio of 1.5 in the lateral direction, a draw-blow moldedbottle drawn at a draw ratio of 3.5 in the lateral direction and at adraw ratio of 3 in the longitudinal direction, and a comparative bottleformed by the above-mentioned direct blow-molding method, respectively.For example, symbol 2122 indicates a biaxially drawn blow-molded bottlecomprising an intermediate layer of EV2, an adhesive layer of AH1 andinnermost and outermost layers of PP1, in which the draw ratio in thelateral direction is 3.5 and the draw ratio in the longitudinaldirection is 3.

From the results shown in Table 3, it will readily be understood thatbiaxially drawn blow-molded bottles are apparently excellent overdirectly blow-molded bottles with respect to the oxygen barrier propertyand transparency, and that although the directly blow-molded bottles areexcellent over biaxially drawn blow-molded bottles with respect to theadhesion strength, the latter bottles are excellent over the formerbottles with respect to the interlaminar peel strength determined by thevisual test, namely the practical peel strength. It will also beunderstood that if the intermediate layer excellent in the barrierproperty to gases such as oxygen is selected so that the above-mentionedrequirements of this invention are satisfied, the oxygen-barrierproperty, transparency and interlaminar peel strength can be remarkablyimproved in the resulting container.

                                      Table 3                                     __________________________________________________________________________                                 Orientation                                                       Hz[%]       Co-efficients                                                     Innermost and                                                                             (innermost and                                                                         Falling Test                                                                             Peel Strength (g/cm of                                                        width)                       Symbol      Interme-                                                                           Outermost   outermost      (number                                                                            Vertical                                                                           Circumferential         of  QO.sub.2,                                                                             diate                                                                              Layers plus layers)        of   direction                                                                          direction               Bottle                                                                            cc/m.sup.2.day.atm                                                                    Layer                                                                              Adhesive Layer                                                                        Bottle                                                                            l  m  n  F.sub.B (%)                                                                         bottles)                                                                           of bottle                                                                          of                      __________________________________________________________________________                                                          bottle                  1111                                                                              7.3     <1   13      14  0.11                                                                             0.12                                                                             0.77                                                                              90   1    126  132                     1112                                                                              6.0     <1    7       8  0.23                                                                             0.32                                                                             0.45                                                                             100   0     32   40                     1113                                                                              8.0     <2   30      33  0.02                                                                             0.03                                                                             0.95                                                                              40   2    221  230                     1121                                                                              7.2     <1   12      13  0.07                                                                             0.09                                                                             0.84                                                                             100   0    151  158                     1122                                                                              6.1     <1    6       6  0.15                                                                             0.19                                                                             0.66                                                                             100   0     29   38                     1123                                                                              9.0     <2   23      24  0.03                                                                             0.02                                                                             0.95                                                                              70   1    230  241                     1211                                                                              7.2     <1   12      13  0.09                                                                             0.10                                                                             0.81                                                                              90   0    131  140                     1212                                                                              6.2     <1    7       7  0.22                                                                             0.31                                                                             0.47                                                                             100   0     22   31                     1213                                                                              8.1     <2   31      33  0.01                                                                             0.02                                                                             0.97                                                                              40   1    218  221                     1221                                                                              7.1     <1   12      14  0.09                                                                             0.11                                                                             0.80                                                                             100   1    142  153                     1222                                                                              6.1     <1    6       7  0.14                                                                             0.18                                                                             0.68                                                                             100   0     63   72                     1223                                                                              8.2     <2   22      23  0.03                                                                             0.04                                                                             0.93                                                                              70   2    292  291                     1311                                                                              7.2     <1   14      15  0.15                                                                             0.14                                                                             0.71                                                                              80   0    141  150                     1312                                                                              6.4     <1    7       8  0.21                                                                             0.25                                                                             0.54                                                                             100   0     69   83                     1313                                                                              8.1     <2   31      32  0.02                                                                             0.03                                                                             0.95                                                                             40    1    289  293                     1321                                                                              7.3     <1   12      12  0.08                                                                             0l08                                                                             0.84                                                                             100   0    150  163                     1322                                                                              6.4     <1    6       6  0.13                                                                             0.18                                                                             0.69                                                                             100   0     70   84                     1323                                                                              8.0     <2   24      25  0.01                                                                             0.04                                                                             0.95                                                                              80   0    288  296                     2111                                                                              2.4     <1   13      15  0.10                                                                             0.11                                                                             0.79                                                                              90   0    148  161                     2112                                                                              2.1     <1    7       9  0.25                                                                             0.32                                                                             0.43                                                                             100   0     58   73                     2113                                                                              2.8     <1   30      32  0.02                                                                             0.03                                                                             0.95                                                                              40   1    291  301                     2121                                                                              2.3     <1   12      13  0.08                                                                             0.09                                                                             0.83                                                                             100   0    150  158                     2122                                                                              2.2     <1    6       7  0.14                                                                             0.19                                                                             0.67                                                                             100   0     59   76                     2123                                                                              2.9     <1   23      25  0.02                                                                             0.03                                                                             0.95                                                                              70   2    293  294                     2211                                                                              2.4     <1   11      12  0.09                                                                             0.09                                                                             0.82                                                                              90   0    146  153                     2212                                                                              2.2     <1    7       7  0.21                                                                             0.28                                                                             0.51                                                                             100   0     53   72                     2213                                                                              3.1     <1   30      32  0.02                                                                             0.03                                                                             0.95                                                                              30   1    289  293                     2221                                                                              2.3     <1   12      13  0.08                                                                             0.08                                                                             0.84                                                                             100   0    151  161                     2222                                                                              2.1     <1    6       7  0.15                                                                             0.20                                                                             0.65                                                                             100   0     59   78                     2223                                                                              2.9     <1   22      23  0.01                                                                             0.04                                                                             0.95                                                                              60   1    291  293                     2311                                                                              2.2     <1   14      15  0.10                                                                             0.08                                                                             0.82                                                                             100   0    145  146                     2312                                                                              2.0     <1    7       8  0.28                                                                             0.32                                                                             0.40                                                                             100   0     52   63                     2321                                                                              2.9     <1   12      14  0.09                                                                             0.08                                                                             0.83                                                                             100   0    138  151                     2322                                                                              2.1     <1    6       7  0.14                                                                             0.20                                                                             0.66                                                                             100   0     72   71                     3111                                                                              2.0     <1   13      15  0.11                                                                             0.09                                                                             0.80                                                                              90   1    109  113                     3112                                                                              35.0    <1    7       7  0.24                                                                             0.29                                                                             0.47                                                                             100   2     19   19                     3121                                                                              2.1     <1   12      13  0.08                                                                             0.09                                                                             0.83                                                                             100   1    111  114                     3122                                                                              1.9     <1    6       7  0.14                                                                             0.20                                                                             0.66                                                                             100   2     20   19                     3211                                                                              2.0     <1   11      13  0.10                                                                             0.09                                                                             0.81                                                                              80   1     99  103                     3212                                                                              21.0    <1    7       8  0.24                                                                             0.28                                                                             0.43                                                                             100   1     17   21                     3221                                                                              2.0     <1   12      14  0.07                                                                             0.08                                                                             0.85                                                                             100   1    115  116                     3222                                                                              2.2     <1    6       7  0.15                                                                             0.19                                                                             0.66                                                                             100   2     21   23                     3311                                                                              1.9     <1   14      15  0.12                                                                             0.11                                                                             0.77                                                                              80   1    103  106                     3312                                                                              24.0    <1    7       7  0.21                                                                             0.27                                                                             0.52                                                                              90   2     19   21                     3321                                                                              2.1     <1   12      15  0.09                                                                             0.09                                                                             0.82                                                                             100   2    139  148                     3322                                                                              53.0    <5    6       7  0.14                                                                              0.018                                                                           0.68                                                                             100   2     21    23                    4111                                                                              95.0    <5   15      17  0.10                                                                             0.11                                                                             0.79                                                                              90   2    117  121                     4112                                                                              78.2    <5   11      12  0.21                                                                             0.27                                                                             0.52                                                                             100   1     31   29                     4121                                                                              91.0    <5   13      18  0.08                                                                             0.09                                                                             0.83                                                                             100   2    117  118                     4122                                                                              76.0    <5   10      12  0.14                                                                             0.16                                                                             0.70                                                                             100   2     29   33                     4211                                                                              83.0    <5   14      15  .12                                                                              0.11                                                                             0.77                                                                              90   1    119  123                     4212                                                                              80.0    <5   11      13  0.23                                                                             0.31                                                                             0.46                                                                             100   1     31   42                     4221                                                                              93.0    <5   14      16  0.09                                                                             0.08                                                                             0.83                                                                             100   0    120  131                     4222                                                                              73.2    <5   11      12  0.15                                                                             0.23                                                                             0.62                                                                             100   1     41   52                     4311                                                                              86.5    <5   15      17  0.13                                                                             0.11                                                                             0.76                                                                              80   1    125  128                     4312                                                                              72.4    <5   12      14  0.22                                                                             0.34                                                                             0.44                                                                             100   0     51   62                     4321                                                                              91.3    <5   15      16  0.08                                                                             0.09                                                                             0.83                                                                              90   0    131  130                     4322                                                                              70.7    <5   10      12  0.14                                                                             0.22                                                                             0.64                                                                             100   1     61   59                     __________________________________________________________________________

EXAMPLE 2

Symmetric 5-layer sheets having a thickness of 0.8 mm and a width of 450mm were formed by using an extruder for forming innermost and outermostlayers, which included a full-flighted screw having a diameter of 65 mmand an effective length of 1430 mm, an extruder for forming adhesivelayers, which included a full-flighted screw having a diameter of 40 mmand an effective length of 880 mm, an extruder for forming intermediatelayers, which included a full-flighted screw having a diameter of 40 mmand an effective length of 880 mm, a T-die equipped with a multichanneladaptor and having a lip width of 0.6 mm and a lip length of 500 mm, anda sheet-forming machine. The ethylene-vinyl alcohol copolymers EV1, EV2,EV3 and EV4 described in Example 1 were used as the intermediatelayer-constituting material. An ethylene-propylene copolymer having adensity of 0.9 g/cc, a melting point of 156° C. as measured according tothe DTA method, a melt index of 1.6 dg/min as measured according to themethod of JIS K-6758 and an ethylene content of 10 mole % was used asthe material of the innermost and outermost layers. An unsaturatedcarboxylic acid-modified ethylene-propylene copolymer having a densityof 0.90 g/cc, a melting point of 154° C. as measured according to theDTA method and a melt index of 2.0 dg/min as measured according to theabove-mentioned method was used as the adhesive layer-constitutingmaterial. The sheet forming operation was carried out by adjusting theamounts of resins extruded from the three extruders so that thethickness ratio of innermost or outermost layer/adhesivelayer/intermediate layer was as close to 100:1:3 as possible. The soformed 4 kinds of sheets were heated for about 15 minutes in a hotair-circulated oven having an atmosphere maintained precisely at 155° C.and they were formed into cups having a diameter of 85 mm, a height of50 mm, an inner capacity of 300 cc and a unit weight of 9 to 10 g/cupaccording to the plug assist vacuum forming method disclosed in thespecification of co-pending U.S. application Ser. No. 750,376.

For comparison, cylindrical cups having the same dimensions as describedabove were formed from the above-mentioned 4 kinds of sheets accordingto the conventional sheet-blowing method, in which the sheetsas-extruded from the T-die and in the molten state were blow-molded.

Cups formed according to the plug assist vacuum forming method (solidphase forming method) using EV1 as the intermediate layer are designatedas "SP1", and cups formed by the molten sheet blow-molding method usingEV1 are designated as "SB1". Similarly, cups formed by using EV2, EV3and EV4 according to the plug assist vacuum forming method aredesignated as "SP2", "SP3" and "SP4", respectively, and cups formed byusing EV2, EV3 and EV4 according to the molten sheet blow-molding methodare designated as "SB2", SB3" and "SB4", respectively.

With respect to each of the foregoing 8 kinds of cups, the oxygentransmission rate (QO₂), the haze (Hz) and the orientation coefficients(l, m and n) were determined according to the methods described inExample 1. Further, 10 sample cups were chosen from each kind of cups,and 340 g of an aqueous solution of table salt was filled in each cup.The filled cups were allowed to stand in an atmosphere maintained at -1°C. over 3 nights and days, and immediately, the cups were subjected tothe free vibration test under conditions of a vibration frequency of 400cpm, a vibration amplitude of 20 mm and an acceleration of 1.8 G for 30minutes by using a Matsudaira type vibration tester and the number (N)of broken cups were counted. Further, occurrence of delamination wasvisually tested by a panel of 5 men (the occurrence of delamination wasevaluated based on an average number (ADN) of cups where delaminationtook place). The thickness uneveness of the intermediate layer in moldedcups was examined in both the vertical and circumferential direction ofthe cup and standard deviations δL and δH were determined. Results ofthese tests are shown in Table 4.

As will be apparent from the results shown in Table 4, the solid phasepressure-formed cups are excellent over directly melt-molded cups withrespect to the oxygen-barrier property and transparency. It will also beunderstood that if the intermediate layer is selected so that therequirements of this invention are satisfied, the resulting cups(samples SP1 and SP2) are much excellent in the interlaminar peelstrength and the thickness uniformity of the intermediate layer.

                                      Table 4                                     __________________________________________________________________________                      H.sub.2 [%]                                                                   Innermost and                                                                            Orientation Coefficients                                      Interme-                                                                           Outermost  (innermost and outermost                                                                   Results of                                                                            Thickness Unevenness                                                          of                          Symbol                                                                             QO.sub.2,                                                                             diate                                                                              Layers plus                                                                              layers)      Vibration Test                                                                        Intermediate Layer          of Cup                                                                             cc/m.sup.2.day.atm                                                                    Layer                                                                              Adhesive Layer                                                                        Cup                                                                              l    m    n  N   ADN δL                                                                            δH              __________________________________________________________________________    SP1  8.3     <1    7       8 0.31 0.13 0.56                                                                             0   0   0.20  0.09                  SP2  3.1     <1    6       7 0.41 0.09 0.50                                                                             0   0   0.15  0.09                  SP3  3.0     <1    6       7 0.29 0.15 0.56                                                                             0   2   0.23  0.10                  SP4  93.2    <1   16      18 0.32 0.15 0.53                                                                             0   1   0.62  0.31                  SB1  13.2    <1   23      24 0.03 0.01 0.96                                                                             0   1   0.21  0.13                  SB2  10.1    <2   22      22 0.04 0.02 0.94                                                                             1   1   0.22  0.12                  SB3  9.6     <2   21      22 0.02 0.01 0.97                                                                             0   2   0.20  0.15                  SB4  142     <2   23      24 0.03 0.01 0.96                                                                             1   3   0.21  0.11                  __________________________________________________________________________

EXAMPLE 3

By using the same molding equipment as used in Example 1, symmetricfive-layer parisons composed of three kinds of resins were prepared, andbottles having a symmetric 5-layer structure were formed from theseparisons according to the sequent biaxial draw-blow forming method inwhich the drawing operation was carried out at 159° C. at a draw ratioof 3 in the longitudinal direction and at a draw ratio of 3.5 in thelateral direction. An ω-aminocaproic acid polymer (N1) having a meltingpoint of 223° C. as measured according to the DTA method, a relativeviscosity of 1.9 as measured with respect to a solution of 1 g of thepolymer in 100 cc of 98% concentrated sulfuric acid and an oxygenpermeability of 4.0×10⁻¹² cc.cm/cm². sec.cmHg as measured at atemperature of 37° C. and a relative humidity of 0% and acaprolactam/hexamethylene diammonium adipate copolymer (N2) having amelting point of 163° C. as measured according to the DTA method, arelative viscosity of 3.4 as measured in the same manner as describedabove, an oxygen permeability of 3.5×10⁻¹² cc.cm/cm².sec.cmHg asmeasured in the same manner as described above and a caprolactamconcentration of 81 mole % were used as the intermediatelayer-constituting material. An unsaturated carboxylic acid-modifiedpolypropylene having a density of 0.90 g/cc and a melting point of 156°C. as measured according to the DTA method was used as the material ofthe adhesive layer adjacent to the intermediate layer. An isotacticpolypropylene having a density of 0.909 g/cc and a melting point of 160°C. as measured according to the DTA method was used as the materialconstituting the innermost and outermost layers.

For comparison, with respect to each of the foregoing two combinationsof resins, in the same manner as described in Example 1, bottles wereformed from multi-layer parisons extruded from the 5-ply die and stillin the molten state according to the direct blow molding method.

Configurations of the so formed 4 kinds of bottles were the same asthose described in Example 1. The amounts of resins extruded from thethree extruders were adjusted so that the thickness ratio of innermostor outermost layer/adhesive layer/intermediate layer was as close to100:2:1 as possible.

With respect to each of these 4 kinds of bottles, the oxygentransmission rate (QO₂), haze (Hz), orientation coefficients, fallingstrength (F_(B)) and interlaminar peel strength were determinedaccording to the same methods as described in Example 1, and the number(N) of broken bottles and occurrence of delamination at the vibrationtest and the standard deviations δL and δH indicating the thicknessunevenness of the intermediate layer were determined according to thesame methods as described in Example 2. Results of these tests are shownin Table 5. In Table 5, bottle symbols indicate the following bottles:

BO1:

Biaxially drawn blow-formed bottles containing N1 as the intermediatelayer-constituting material.

BO2:

Biaxially drawn blow-formed bottles containing N2 as the intermediatelayer-constituting material.

DO1:

Directly blow-molded bottles (formed by blow molding of molten parisons)containing N1 as the intermediate layer-constituting material.

DO2:

Directly blow-molded bottles containing N2 as the intermediatelayer-constituting material.

From the results shown in Table 5, it will readily be understood thatBO2 bottles formed by selecting the intermediate layer so that therequirements of the present Invention are satisfied are much excellentin the oxygen-barrier property, falling strength, strength anddelamination resistance at the vibration test and thickness uniformityof the intermediate layer.

                                      Table 5                                     __________________________________________________________________________                                  Orientation              Thickness                                H2[%]   Coefficients           Unevenness                                     Innermost and                                                                         innermost and                                                                     Falling Test Results                                                                   Vibration Of Inter-                    Symbol       Interme-                                                                           Outermost   Outermost     N (number                                                                          Test  Medicare               of   Q O.sub.2,                                                                            diate                                                                              Layers plus layers)       of broken                                                                          Results                                                                             Layer                  Bottle                                                                             cc/m.sup.2 .day.atm                                                                   Layer                                                                              Adhesive Layer                                                                        Bottle                                                                            l  m) n  FB (%)                                                                             bottles)                                                                           N ADN δL                                                                          δH           __________________________________________________________________________    B01  56.2    <2    7       8  0.23                                                                             0.31                                                                             0.46                                                                             100  3    0 1   0.35                                                                              0.12               B02  19.1    <2    6       7  0.22                                                                             0.30                                                                             0.48                                                                             100  0    0 0   0.15                                                                              0.09               D01  41.5    <5   31      33  0.02                                                                             0.01                                                                             0.97                                                                              40  0    0 0   0.21                                                                              0.10               D02  36.9    <5   32      34  0.03                                                                             0.02                                                                             0.95                                                                              50  1    1 1   0.20                                                                              0.11               __________________________________________________________________________

EXAMPLE 4

Sheets having a thickness of 0.5 mm and a width of about 400 mm andhaving a symmetric 5-layer structure were prepared by using a knownextruding and sheet-forming machine.

The same ω-aminocaproic acid polymer (6-nylon, N1) as used in Example 3,6,6-nylon (N3) having a melting point of 265° C. according to the DTAmethod in which the temperature-elevating rate was 10° C./min and anoxygen permeability of 0.69×10⁻¹² cc.cm/cm².sec.cmHg as measured at atemperature of 37° C. and a relative humidity of 0%, and an 80/20(weight ratio) mixture (N13) of 6-nylon and 6,6-nylon having a meltingpoint of 228° C. as measured according to the above DTA method and anoxygen permeability of 2.2×10⁻¹² cc.cm/cm².sec.cmHg were used as theintermediate layer-constituting resin. A 4-methyl-pentene-1 polymer(manufactured and sold under tradename "TPX" by ICI) having a density of0.835 g/cc, a melting point of 228° C. as measured according to theabove DTA method and a melt index of about 7.0 as measured underconditions of a load of 5 kg and a temperature of 265° C. was used asthe resin constituting innermost and outermost layers. Adhesivepolypropylene (manufactured and sold under tradename "MODIC" byMitsubishi Petrochemical) having a density of 0.90 g/cc, a melting pointof 153° C. as measured according to the above DTA method and a meltindex of 2.4 as measured according to the method of JIS K-6760 was usedas the resin constituting an adhesive layer interposed between theinnermost or outermost layer and the intermediate layer. In the samemanner as described in Example 2, the sheet-forming operation wascarried out while adjusting the rotation number of the screw so that theinnermost or outermost layer/adhesive layer/intermediate layer thicknessratio was as close to as 100:5:10 as possible.

The so prepared three kinds of sheets were sufficiently heated in a hotair-circulated oven installed with an infrared heater maintainedprecisely at a molding temperature indicated in Table 6, and they wereformed into cylindrical cups having a diameter of 85 mm, a height of 50mm, an inner capacity of 300 cc and a unit weight of 9 to 10 g per cupaccording to the known plug assist air-pressure forming method.

For comparison, the foregoing three kinds of sheets were heated at 250°C. in the above-mentioned oven just after formation of the sheets andthey were formed into cylindrical cups having the same configurations asdescribed above according to the plug assist air-pressure formingmethod.

With respect to each of the so obtained 6 kinds of cups, the peelstrength, the thickness unevenness in both the vertical andcircumferential directions of the cup and the standard deviations δL andδH were determined to obtain results shown in Table 6.

As will be apparent from the results shown in Table 6, as compared withthe normal heat forming method conducted at 265° C., in the solid phasepressure forming method conducted at 226° C., resin combinationssatisfying the requirements of the present invention give generallybetter results.

In the above-mentioned DTA method, the melting-initiating temperature(the temperature at which melting endotherm takes place in the DTAthermogram) of 6-nylon (N1) was 209° C. and the melting-endingtemperature (the temperature at which melting endotherm is completed inthe DTA thermogram) was 229° C. The melting-initiating temperature ofthe blend (N13) of 6-nylon and 6,6-nylon was 203° C. and themelting-ending temperature of the nylon blend was 232° C. Themelting-initiating and melting-ending temperatures of 6,6-nylon were246° C. and 268° C., respectively. Accordingly, when the forming wascarried out at 226° C., 6-nylon (N1) and nylon blend (N13) were in thesemi-molten state and 6,6-nylon was maintained at the forming step at atemperature much lower than the melting-initiating temperature (246°C.).

                  Table 6                                                         ______________________________________                                                    Peel Strength                                                                 (g/l cm width)                                                                                 Adhesive                                         Intermediate                                                                           Forming  Intermediate                                                                             layer-                                           Layer-   Temper-  layer-     innermost                                                                             Thickness                                Constituting                                                                           ature    adhesive   or outermost                                                                          Unevenness                               Material (°C.)                                                                           layer      layer   δL                                                                           δH                            ______________________________________                                        N1       226      935        410     0.15 0.09                                N3       226       15         20     0.20 0.12                                N13      226      930        420     0.13 0.10                                N1       268      930        420     0.42 0.12                                N3       268      1030       380     0.50 0.11                                N13      268      920        480     0.43 0.15                                ______________________________________                                    

EXAMPLE 5

Four kinds of sheets prepared in Example 2 were subjected to coldrolling at a rolling speed of about 5 m/min at room temperture by usinga roll. The sheet thickness after the cold rolling was about 0.40 mm.The cold-rolled sheets were heated at a tray-forming temperatureprecisely controlled to a level indicated in Table 7 and then formed inrectangular trays having a length of 140 mm, a width of 100 mm and adepth of 25 mm under a forming pressure of 5 to 9 Kg/cm² according tothe known plug assist air-pressure forming method.

For comparison, the foregoing 4 kinds of cold-rolled sheets weresufficiently heated at about 210° C. and formed in rectangular trayshaving the same dimensions as described above according to the plugassist air-pressure forming method.

With respect to each of the foregoing 4 kinds of sheets before coldrolling, the foregoing 4 kinds of cold-rolled sheets and the foregoing 8kinds of formed trays, in the same manner as described in Example 1, thepeel strength and orientation coefficients (l, m and n) were determined.With respect to each of the foregoing 8 kinds of trays, the haze (Hz)was determined according to the method of JIS K-6714. Results are shownin Table 7.

As will be apparent from the results shown in Table 7, even when rolledsheets are formed into trays, if the requirements of the presentinvention are satisfied, the properties of trays can be remarkablyimproved. It will also be understood that even if properties areimproved by rolling, when normal heat forming is conducted on rolledsheets, the improved properties, for example, the peel strength betweenthe intermediate and adhesive layers and the haze, are lowered to levelsbefore rolling.

                                      Table 7                                     __________________________________________________________________________              Tray-                                                                              Peel Strength*                                                           Forming                                                                            (g/l cm width) Orientation Coeff-**                            Interme-  Tempera-                                                                           intermediate                                                                         adhesive layer-                                                                       cients (innermost                               diate     ture layer-adhes-                                                                         innermost or                                                                          and outermost layers)                                                                    Haze (Hz)                            Sheet                                                                              Layer                                                                              (°C.)                                                                       ive layer                                                                            outermost layer                                                                       l   m                                                                              n     (%)                                  __________________________________________________________________________    Unrolled                                                                           EV1       285    not peeled                                                                            0.02                                                                              0.01                                                                              0.97                                                                             21                                   Sheet                                                                              EV2       320    "       0.01                                                                              0.03                                                                              0.96                                                                             20                                        EV3       430    "       0.02                                                                              0.01                                                                              0.97                                                                             21                                        EV4       250    "       0.03                                                                              0.02                                                                              0.95                                                                             19                                   Cold-                                                                              EV1       420    "       0.20                                                                              0.08                                                                              0.72                                                                             12                                   Rolled                                                                             EV2       525    "       0.21                                                                              0.07                                                                              0.72                                                                             13                                   Sheet                                                                              EV3       930    "       0.21                                                                              0.06                                                                              0.73                                                                             11                                        EV4       390    "       0.20                                                                              0.05                                                                              0.75                                                                             15                                        EV1  155  415    "       0.38                                                                              0.18                                                                              0.44                                                                              8                                        EV2  155  520    "       0.45                                                                              0.15                                                                              0.40                                                                              7                                        EV3  155  <10*** "       0.35                                                                              0.18                                                                              0.47                                                                              7                                        EV4  155  395    "       0.37                                                                              0.17                                                                              0.46                                                                             13                                        EV1  210  283    "       0.03                                                                              0.02                                                                              0.95                                                                             18                                        EV2  210  310    -       0.03                                                                              0.02                                                                              0.95                                                                             19                                        EV3  210  450    "       0.02                                                                              0.01                                                                              0.95                                                                             21                                        EV4  210  310    "       0.03                                                                              0.01                                                                              0.96                                                                             20                                   __________________________________________________________________________

EXAMPLE 6

Symmetric 7-layer sheets composed of four resins were prepared from thesame resin combination as that used in Example 1 for formation ofinnermost, outermost, intermediate and adhesive layers, andadditionally, sheet scraps formed at the forming step in this Exampleand scraps formed by crushing defective cups formed in this Example by acrusher were used as the resin material for formation of layersinterposed between the innermost layer and adhesive layer and betweenthe outermost layer and adhesive layer. From these resin materials,symmetric 7-layer sheets having a thickness of about 0.8 mm and a widthof 450 mm were molded by using the same extruder for formation ofinnermost and outermost layers, the same extruder for formation ofadhesive layers, the same extruder for formation of intermediate layersand the same sheet-winding machine as used in Example 2, andadditionally, an extruder for formation of intervening layers, which wasinstalled with a full-flighted screw having a diameter of 40 mm and aneffective length of 880 mm, and a sheet extrusion molding machinecomprising a multi-channel adaptor and a T-die having a lip width of 0.8mm and a lip length of 500 mm were used for the sheet-forming operation.The screw rotation numbers of the four extruders were adjusted so thatin the molded sheets, the thickness ratio of innermost or outermostlayer/intervening layer/adhesive layer/intermediate layer was as closeto 100:20:5:10 as possible.

The so obtained 4 kinds of sheets were sufficiently heated at 155° C.and then formed into cylindrical cups having the same configurations andunit weight as those of the cups prepared in Example 2 according to theknown plug assist air-pressure forming method. For comparison, thesesheets were formed into cylindrical cups having the same configurationsand unit weight as above according to the sheet blow molding method asin Example 2.

Cups prepared by plug assist air-pressure forming (solid phase forming)by using EV1 as the intermediate layer-constituting resin weredesignated as "SR1" and cups prepared by sheet blow molding of moltensheets containing EV1 as the intermediate layer-constituting resin weredesignated as "SBB1". Similarly, cups formed by plug assist air-pressureforming by using EV2, EV3 and EV4 and cups formed by sheet blow moldingby using EV2, EV3 and EV4 were designated as "SPR2", "SPR3", "SPR4","SBB2", "SBB3" and "SBB4", respectively.

With respect to each of these 8 kinds of cups, the oxygen transmissionrate (QO₂), haze (Hz), orientation coefficients (l, m and n), vibrationresistance (N, ADN) and thickness unevenness (δL and δH) in theintermediate layer were determined in the same manner as described inExample 2 to obtain results shown in Table 8.

From the results shown in Table 8, it will readily be understood thatthe transparency of cups obtained in this Example is inferior to that ofthe cups obtained in Example 2 because of the presence of interveninglayers of scraps, but a similar tendency is observed in this Examplewith respect to other items and cups having excellent properties can beobtained if the requirements of this invention are satisfied.

                                      Table 8                                     __________________________________________________________________________                  Orientation Coeffi-                                                                       Vibration                                               QO.sub.2, cients (innermost                                                                         Test  Thickness Uneveness                           Symbol                                                                            cc/m.sup.2.day.                                                                     HZ(%)                                                                             and outermost layers)                                                                     Results                                                                              in Intermediate Layer                        of Cup                                                                            atm   (cup)                                                                             γ                                                                           m   n   N ADN δL                                                                              δH                              __________________________________________________________________________    SPR1                                                                              1.7   12  0.32                                                                              0.10                                                                              0.58                                                                              0 0   0.19    0.09                                  SPR2                                                                              0.6    9  0.39                                                                              0.10                                                                              0.51                                                                              0 0   0.14    0.09                                  SPR3                                                                              0.6    9  0.31                                                                              0.14                                                                              0.55                                                                              0 2   0.20    0.11                                  SPR4                                                                              20.2  18  0.32                                                                              0.15                                                                              0.53                                                                              0 1   0.53    0.29                                  SBR1                                                                              3.8   26  0.03                                                                              0.01                                                                              0.96                                                                              0 1   0.21    0.13                                  SBR2                                                                              3.2   24  0.04                                                                              0.01                                                                              0.95                                                                              1 2   0.19    0.14                                  SBR3                                                                              2.8   25  0.02                                                                              0.02                                                                              0.96                                                                              1 1   0.20    0.13                                  SBR4                                                                              31.0  27  0.04                                                                              0.01                                                                              0.95                                                                              1 2   0.21    0.12                                  __________________________________________________________________________

EXAMPLE 7

Bottom-less laminate pipes (laminate parisons) having a symmetric5-layer structure of outer layer/adhesive layer/oxygen-barrier layer(intermediate layer)/adhesive layer/inner layer were prepared by usingan extruder for formation of intermediate layers having a diameter of 40mm, an effective length of 880 mm and one melt channel passage, anextruder for formation of adhesive layers having a diameter of 40 mm, aneffective length of 880 mm and 2 melt channel passages, an extruder forformation of outer and inner layers having a diameter of 65 mm, aneffective length of 1430 mm and 2 melt channel passages and a 5-ply diefor co-extrusion.

An isotactic homopolypropylene having a melt index of 0.5 g/10 min asmeasured according to the method of ASTM D-1238 (data of melt indexgiven hereinafter are those as determined by the same method), a densityof 0.91 g/cc as measured according to the method of ASTM D-1505 (data ofdensity given hereinafter are those determined by the same method) and amelting point of 165° C. as measured according to the DTA method wasused as the resin constituting the outer and inner layers. A modifiedlow density polyethylene (manufactured and sold under tradename "MODIC"by Mitsubishi Petrochemical) having a melt index of 2.0 g/10 min, adensity of 0.92 g/cc, a melting point of 113° C. as measured accordingto the DTA method and a carbonyl group concentration of 180 millimolesper 100 g of the polymer was used as the adhesive layer-constitutingresin. An ethylene-vinyl alcohol copolymer having an ethylene content of35 mole %, a vinyl alcohol content of 64.5 mole %, a residual vinylacetate content of 0.5 mole %, a melting point of 164° C. as measuredaccording to the DTA method (temperature-elevating rate=10° C./min) andan oxygen permeability of 0.16×10⁻¹² cc.cm/cm².sec.cmHg as measured at atemperature of 37° C. and a relative humidity of 0% was used as theoxygen-barrier intermediate layer. Parisons of this multi-layerstructure were designated as "parisons A".

Bottomless laminate pipes (laminate parisons) having the same symmetric5-layer structure as described above were prepared by using the sameco-extrusion equipment system as described above. The same resins asdescribed above were used for formation of outer, inner and intermediatelayers, but as the adhesive layer-constituting resin, there was employeda modified polypropylene (manufactured and sold under tradename "MODIC"by Mitsubishi Petrochemical) having a melt index of 2.0 g/10 min, adensity of 0.91 g/cc, a melting point of 160° C. as measured accordingto the DAT method and a carbonyl group concentration of 167 millimolesper 100 g of the polymer. The pipes (parisons) were designated as "pipesB".

In each of the pipes A and B, the total thickness was about 10 mm, theinner diameter was 30 mm and the length was 30 mm, and the thicknessratio of outer layer/adhesive layer/intermediate layer/adhesivelayer/inner layer was 1:1/20:1/50:1/20:1.

The pipes (parisons) A and B were heated for 35 minutes in an atmospheremaintained at 158°±0.5° C. Both the ends of each pipe were climped byclamps, and the pipe was drawn in the longitudinal direction. Then, thepipe was gripped by a mold for blow molding and air was introduced underpressure from one end to inflate the parison in the lateral direction.Thus, biaxially drawn blow bottles having a symmetric 5-layer structurewere prepared. In the so obtained bottles, the inner diameter was 100mm, the height is 150 mm, the average thickness of the bottle wall was0.6 mm, the inner capacity was about 1180 cc and the unit volume was0.31 dl/g. The bottles had a cylindrical shape, and it was confirmedthat in each bottle, the multi-layer structure was the same as theabove-mentioned structure of the parison. Bottles prepared from parisonsA and from parisons B were designated as "bottles AB" and "bottles BB",respectively.

With respect to each of the so obtained bottles, the oxygen permeability(QO₂) was determined according to the method described in JapanesePatent Publication No. 11263/77, and the haze (Hz) was determinedaccording to the method of JIS K-6714. Further, the bottles weresubjected to the falling test described below to determine the impactresistance (SB) and delamination resistance (LB). The falling test wasconducted in the following manner.

Twenty bottles were optionally chosen from each of groups AB and BB ofbottles, and 1150 cc of an fqueous solution of table salt was filled ineach sample bottle. The filled bottles were allowed to stand over 3 daysand nights in an atmosphere maintained at -1° C. and they were let tofall on a concrete fllor from a height of 100 cm in an atmospheremaintained at 20° C. so that bottoms of the bottles hit on the concretefloor, and the falling strength (impact resistance represented by S_(B)=100×[20-S₁ ]/20 in which S₁ represents a number of bottles broken atthe first falling test) was determined. Further, with respect to N ofbottles which were not broken in the above falling test, occurrence ofdelamination in the bottom portion, barrel portion, shoulder portion andmouth portion was visually checked by a panel of 5 men, and thedelamination resistance (L_(B) =100×[N-L₁ ]/N in which L₁ represents anumber of bottles in which it was judged that delamination took place,among N of bottles which were not broken at the first falling test) wasdetermined. Obtained results are shown in Table 9.

As will be apparent from the results shown in Table 9, there is nosubstantial difference between bottles AB and BB with respect to theoxygen permeability (O₂) and haze (Hz), but bottles AB are apparentlyexcellent over bottles BB with respect to the measured value of impactstrength (S_(B)) and delamination resistance (L_(B)). Thus, it it seenthat blow bottles AB formed by heating formed pipes to melt the adhesivelayer-constituting resin and then biaxially drawing the pipes are muchexcellent over blow bottles BB formed by conducting biaxial drawingwithout melting the adhesive resin layer-constituting resin with respectto the impact resistance and delamination resistance.

When pipes B were heated for 20 minutes in an atmosphere maintained at198°±1° C., the pipes were molten and they could not retain theirshapes. Accordingly, in this case biaxial drawing was impossible.

EXAMPLE 9

    ______________________________________                                                       Bottle AB  Bottle BB                                           ______________________________________                                        Oxygen Permeability                                                                            10.0         10.4                                            (QO.sub.2, cc/m.sup.2.day.atm)                                                Haze (HZ, %)     8.4          8.5                                             Impact Resistance (S.sub.B, %)                                                                 90           60                                              Delamination Resistance                                                                        72.2         0                                               (L.sub.B, %                                                                   ______________________________________                                    

EXAMPLE 8

Sheets having a symmetric 5-layer structure of outermost layer/adhesivelayer/oxygen-barrier layer (intermediate layer)/adhesive layer/innermostlayer were prepared by using an extruder for formation of outermost andinnermost layers, which was installed with a full-flighted screw havinga diameter of 65 mm and an effective length of 1430 mm and had 2 dividedflow passages (melt channels), an extruder for formation of adhesivelayers, which was installed with a full-flighted screw having a diameterof 40 mm and an effective length of 880 mm and had 2 divided meltchannels, an extruder for formation of intermediate layers, which wasinstalled with a full-flighted screw having a diameter of 40 mm and aneffective length of 880 mm, a 5-ply T-die having a lip width of 0.6 mmand a lip length of 500 mm and a sheet-forming machine.

The same ethylene-vinyl alcohol copolymers EV1 and EV2 as used inExample 1 and an ethylene-vinyl alcohol copolymer (EV-5) having anethylene content of 63 mole %, a vinyl alcohol content of 37 mole %, amelting point of 128° C. as the DTA method described in Example 1 and anoxygen permeability of 4.4×10⁻¹² cc.cm/cm².sec.cmHg as measured underthe conditions described in Example 1 were used as the intermediatelayer-constituting resin. Low-pressure polyethylene (HDPF) having adensity of 0.955 g/cc, a melting point of 131° C. as measured accordingto the DTA method and a melt index of 0.3 g/10 min as measured accordingto the method of JIS K-6760 and medium low-pressure polyethylene (MDPE)having a density of 0.935 g/cc, a melting point of 122° C. as measuredaccording to the DTA method and a melt index of 1.0 g/10 min as measuredaccording to the above method were used as the resin constituting theinnermost and outermost layers. A modified low density polyethylene(manufactured and sold under tradename "MODIC" by MitsubishiPetrochemical) having a density of 0.92 g/cc, a melting point of 114° C.as measured according to the DIA method, a melt index of 0.3 g/10 min asmeasured according to the above method and a carbonyl groupconcentration of 48 millimoles per 100 g of the polymer was used as theadhesive layer-constituting resin.

In the so formed sheets, the thickness was about 0.8 mm and the widthwas about 450 mm. At the sheet-forming step, the rotation rates of thescrews of the three extruders were adjusted so that the thickness ratioof innermost or outermost layer/adhesive layer/intermediate layer was asclose to 100:5:10 as possible.

The so prepared 6 kinds of sheets were cold-rolled at room temperatureat a rolling speed of about 5 m/min by using a pair of rolls having adiameter of 10 mm and a width of 500 mm. The cold-rolled sheets had athickness of about 0.35 mm. Then, the rolled sheets were sufficientlyheated in a hot air-circulated oven maintained precisely at a formingtemperature indicated in Table 10. Then, the sheets were formed under apressure of 5 to 9 Kg/cm² into rectangular trays having a length of 140mm, a width of 100 mm and a depth of 25 mm according to the known plugassist air-pressure forming method.

For comparison, the foregoing 6 kinds of cold-rolled sheets were heatedsufficiently at 190° or 200° C. and then, they were formed intorectangular trays having the same configurations as described aboveaccording to the plug assist air-pressure forming method.

With respect of each of 6 kinds of sheets before cold rolling, 6 kindsof cold-rolled sheets and 12 kinds of so prepared trays, specimenshaving a width of 10 mm and a length of 50 mm were cut off, theinterlaminar peel strength (intermediate layer-adhesive layer andadhesive layer-innermost or outermost layer) was measured at a peelingspeed of 100 mm/min in an atmosphere maintained at a temperature of 20°C. and a relative humidity of 60%, and the orientation coefficients (l,m and n) of the intermediate layer were determined according to thefluorescent method described hereinbefore. Further, with respect to 12kinds of the resulting trays, the haze (Hz) was determined according tothe method of JIS K-6714. Test results are shown in Table 10.

As will be apparent from the results shown in Table 10, trays preparedfrom resin combinations HDPE-EV1, HDPE-EV2 and MDPE-EV5 meeting therequirements of the present invention are collectively excellent.

                                      Table 10                                    __________________________________________________________________________     Layer-Constituting     Peel Strength* [g/cm width]                           Resins            Tray- Interme-                                                                             Adhesive                                                  Inner- Forming                                                                             diate  Layer Inner-                                        Interme-                                                                            most and                                                                             Temper-                                                                             layer- most or                                             diate Outermost                                                                            ature adhesive                                                                             Outermost                                      Sheet                                                                              Layer Layers (°C.)                                                                        Layer  Layer                                          __________________________________________________________________________    Unrolled                                                                           EV1   HDPE          198   not peeled                                     Sheet                                                                              "     MDPE          220   not peeled                                          EV2   HDPE          119   not peeled                                          "     MDPE          184   not peeled                                          EV5   HDPE          189   not peeled                                          "     MDPE          168   not peeled                                     Cold-                                                                              EV1   HDPE         1020   not peeled                                     Rolled                                                                             "     MDPE         1130   not peeled                                     Sheet                                                                              EV2   HDPE         1060   not peeled                                          "     MDPE         1100   not peeled                                          EV5   HDPE         1090   not peeled                                          "     HDPE          980   not peeled                                     Cold-                                                                              EV1   HDPE   129   1005   not peeled                                     Rolled                                                                             "     MDPE   118    150   not peeled                                     Sheet                                                                              EV2   HDPE   129    655   not peeled                                          "     MDPE   118    135   not peeled                                          EV5   HDPE   129   1030   not peeled                                          "     MDPE   118    950   not peeled                                          EV1   HDPE   198    160   not peeled                                          "     MDPE   198    173   not peeled                                          EV2   HDPE   200   110    not peeled                                          "     MDPE   200   170    not peeled                                          EV5   HDPE   195   185    not peeled                                          "     MDPE   195    158   not peeled                                     Layer Constituting                                                             Resins           Orientation                                                            Inner- Coefficients**                                              Interme-   most and                                                                             (Innermost and                                              diate      Outermost                                                                            Outermost Layers)                                                                         Haze (Hz)                                       Sheet                                                                              Layer Layers l   m   n   (%)                                             __________________________________________________________________________    Unrolled                                                                           EV1   HDPE   0.02                                                                              0.01                                                                              0.97                                                                              --                                              Sheet                                                                              "     MDPE   0.01                                                                              0.01                                                                              0.98                                                                              --                                                   EV2   HDPE   0.02                                                                              0.01                                                                              0.97                                                                              --                                                   "     MDPE   0.01                                                                              0.02                                                                              0.97                                                                              --                                                   EV5   HDPE   0.01                                                                              0.01                                                                              0.98                                                                              --                                                   "     MDPE   0.03                                                                              0.01                                                                              0.96                                                                              --                                              Cold-                                                                              EV1   HDPE   0.19                                                                              0.08                                                                              0.73                                                                              --                                              Rolled                                                                             "     MDPE   0.17                                                                              0.09                                                                              0.74                                                                              --                                              Sheet                                                                              EV2   HDPE   0.21                                                                              0.06                                                                              0.73                                                                              --                                                   "     MDPE   0.22                                                                              0.09                                                                              0.69                                                                              --                                                   EV5   HDPE   0.18                                                                              0.10                                                                              0.72                                                                              --                                                   "     MDPE   0.19                                                                              0.07                                                                              0.74                                                                              --                                              Cold-                                                                              EV1   HDPE   0.19                                                                              0.11                                                                              0.70                                                                              42                                              Rolled                                                                             "     MDPE   0.13                                                                              0.10                                                                              0.72                                                                              30                                              Sheet                                                                              EV2   HDPE   0.22                                                                              0.11                                                                              0.67                                                                              --                                                   "     MDPE   0.23                                                                              0.09                                                                              0.68                                                                              --                                                   EV5   HDPE   0.19                                                                              0.10                                                                              0.71                                                                              --                                                   "     MDPE   0.20                                                                              0.08                                                                              0.72                                                                              --                                                   EV1   HDPE   0.03                                                                              0.02                                                                              0.95                                                                              78                                                   "     MDPE   0.02                                                                              0.04                                                                              0.94                                                                              62                                                   EV2   HDPE   0.04                                                                              0.03                                                                              0.93                                                                              82                                                   "     MDPE   0.01                                                                              0.04                                                                              0.95                                                                              51                                                   EV5   HDPE   0.03                                                                              0.02                                                                              0.95                                                                              79                                                   "     MDPE   0.04                                                                              0.03                                                                              0.93                                                                              53                                              __________________________________________________________________________     Notes                                                                         *: average value (sample number = 10)                                         **: l direction of the tray corresponds to the rolling direction of the       starting sheet and to the direction of the long axis of the rectangular       shape of the tray.                                                       

EXAMPLE 9

Symmetric 5-layer sheets having a thickness of 0.8 mm and a width of 450mm were formed by using the extruding and sheet-forming equipment systemdescribed in Example 8. The rotation numbers of the screws were adjustedas in Example 8 so that the thickness ratio of innermost or outermostlayer/adhesive layer/intermediate layer was as close to 100:5:10 aspossible.

The same ethylene-vinyl alcohol copolymers EV1 and EV2 as used inExample 1 were used as the intermediate layer-constituting resin.Polybutene-1 having a density of 0.915 g/cc, a melting point of 129° C.as measured according to the DTA method and a melt flow index of 0.1g/10 min as measured according to the method of ASTM D1238 (condition E)was used as the resin constituting the innermost and outermost layers.

A modified ethylene-vinyl acetate copolymer (manufactured and sold undertradename "MODIC" by Mitsubishi Petrochemical) having a density of 0.94g/cc, a melting point of 93° C. as measured according to the DTA method,a melt index of 2.0 g/10 min as measured according to the method of JISK-6760 and a carbonyl group concentration of 240 millimoles per 100 g ofthe polymer was used as the resin constituting the adhesive layerbetween the intermediate layer and the innermost or outermost layer.

Two kinds of the so prepared sheets were sufficiently heated in a hotair-circulated oven maintained precisely at a forming temperatureindicated in Table 11 and installed with an infrared heater, and then,they were formed into cylindrical cups having a diameter of 85 mm, aheight of 50 mm, an inner capacity of 300 cc and a unit weight of 9 to10 g per cup according to the known plug assist air-pressure formingmethod.

For comparison, the foregoing 2 kinds of sheets were sufficiently heatedat 190° to 200° C. in the above-mentioned oven and they were formed intocylindrical cups having the same dimensions as described above accordingto plug assist air-pressure forming method.

With respect to each of the so prepared 4 kinds of cups, the oxygenpermeability (QO₂) was determined according to the method described inExample 7. Ten cups were chosen from each of the foregoing 4 kinds ofcups, and 340 g of an aqueous solution of table salt was filled in eachcup and an aluminum lid was attached to each cup by means of a seamer.Then, the cups were allowed to stand in an atmosphere maintained at -1°C. over three days and nights, and immediately, they were let to fall ona concrete floor from a height of 3 mm in an atmosphere maintained at20° C. so that the bottoms hit on the concrete floor. The fallingstrength (S_(B)) was calculated according to the method described inExample 7, and the delamination resistance (L_(B) defined in Example 7)was visually evaluated by a panel of 5 men. Obtained results are shownin Table 11.

As will be apparent from the results shown in Table 11, cups excellentin oxygen-barrier property and falling strength can be obtained whenresin combinations including EV1 as the intermediate layer constitutingresin and meeting the requirements of the present invention are used andthe forming temperature is adjusted to 125° C.

                  Table 11                                                        ______________________________________                                        Inter-                                                                        mediate                                                                       Layer- Forming                       Delam-                                   Consti-                                                                              Temper-  Oxygen        Falling                                                                              ination                                  tuting ature    Permeability (QO.sub.2)                                                                     Strength                                                                             Resistance                               Resin  (° C.)                                                                          (cc/m.sup.2 ·day·atm)                                                     (S.sub.B) [%]                                                                        (L.sub.B) [%]                            ______________________________________                                        EV1    125      1.2           100    100                                      EV2    125      0.4           90     90.0                                     EV1    200      2.1           80     87.5                                     EV2    200      0.8           70     71.4                                     ______________________________________                                    

EXAMPLE 10

Symmetric 5-layer sheets having a thickness of about 0.8 mm and a widthof 450 mm were formed by using the extruding and sheet-forming equipmentsystem described in Example 8. The rotation numbers of the screws of theextruders were adjusted so that the thickness ratio of innermost oroutermost layer/adhesive layer/intermediate layer was so close to100:5:10 as possible.

The same ethylene-vinyl alcohol copolymers EV1, EV2 and EV5 as used inExample 8 were employed as the intermediate layer-constituting resin. Apolycarbonate (PC) synthesized from phosgene and bisphenol-A, which hada softening point of 160° C. as measured according to the torsionrigidity measurement method, and poly(methyl methacrylate) (PMMA) havinga glass transition temperature of 115° C. as measured according to theDTA method were used as the resin constituting the innermost andoutermost layers. The same modified ethylene-vinyl acetate copolymer asused in Example 8 was used as the resin constituting the adhesive layerbetween the intermediate layer and the innermost or outermost layer.

The so prepared 6 kinds of sheets were formed into cylindrical cupshaving the same configurations and unit weight as those of the cupsprepared in Example 9 at a forming temperature indicated in Table 12according to the known plug assist air-pressure forming method.

With respect to each of the so formed 6 kinds of cups, the orientationcoefficients (l, m and n) of the intermediate layer were determinedaccording to the above-mentioned fluorescence method, the interlaminarpeel strength between the intermediate layer and adhesive layer wasmeasured according to the method described in Example 8, and thethickness unevenness (standard-deviations δL and δH) in the verticaldirection and circumferential direction of the cup was determined.Obtained results are shown in Table 12.

From the results shown in Table 12, it will readily be understood thatwhen resin combinations meeting the requirements of the presentinvention are employed, cups collectively excellent in variousproperties can be obtained.

                                      Table 12                                    __________________________________________________________________________    Layer-Constituting Resins                                                                  Forming       Thickness                                          Interme-     Tempera-                                                                           Orientation                                                                            Uniformity                                                                          Peel Strength (g/cm                          diate                                                                              Innermost or                                                                          ture Coefficients                                                                           in Cup                                                                              width) (intermediate                         Layer                                                                              outermost layer                                                                       (° C.)                                                                      l  m  n  δL                                                                         δH                                                                         layer-adhesive layer)                        __________________________________________________________________________    EV1  PC      153  0.32                                                                             0.10                                                                             0.58                                                                             0.18                                                                             0.07                                                                             480                                          EV3  PC      153  0.29                                                                             0.12                                                                             0.59                                                                             0.20                                                                             0.10                                                                             <10                                          EV5  PC      153  0.30                                                                             0.09                                                                             0.61                                                                             0.19                                                                             0.15                                                                             235                                          EV1  PMMA    105  0.25                                                                             0.09                                                                             0.66                                                                             0.23                                                                             0.08                                                                             253                                          EV3  PMMA    105  0.27                                                                             0.06                                                                             0.67                                                                             0.25                                                                             0.12                                                                             <10                                          EV5  PMMA    105  0.23                                                                             0.07                                                                             0.70                                                                             0.21                                                                             0.14                                                                             135                                          __________________________________________________________________________

What we claim is:
 1. A process for the preparation of containers whichcomprises forming a multi-layer structure comprising at least one layercomposed of an oxygen-barrier thermoplastic resin having an oxygenpermeability lower than 5.5×10⁻¹² cc.cm/cm².sec.cmHg as measured at 37°C. and at least one layer comprising an orienting thermoplastic resinother than the oxygen-barrier thermoplastic resin by co-melt-extrusion,said two resins being selected so that the requirement represented bythe following formula:

    |T.sub.B -T.sub.O |≦35° C. (1)

wherein T_(B) stands for the melting or softening point (°C.) of saidoxygen-barrier thermoplastic resin and T_(O) stands for the melting orsoftening point (°C.) of said orienting thermoplastic resin, issatisfied; and molding said multi-layer structure into a container at amolding temperature (Tm) satisfying the requirement represented by thefollowing formula:

    |Tm -T.sub.B |≦30° C.      (8)

wherein T_(B) is as defined above and Tm stands for the moldingtemperature (°C.), and under such conditions that orientation of theorienting thermoplastic resin is caused at least in a smallest-thicknessportion of the container.
 2. A process according to claim 1 wherein themulti-layer structure is biaxially oriented at said molding temperature(Tm).
 3. A process according to claim 1 wherein the multi-layer sheet isdrawn into a cup at said molding temperature (Tm).
 4. A process for thepreparation of containers which comprises forming a multi-layerstructure comprising at least one layer composed of an oxygen-barrierthermoplastic resin having an oxygen permeability lower than 5.5×10⁻¹²cc.cm/cm².sec.cmHg as measured at 37° C., at least one layer comprisingan orienting thermoplastic resin other than the oxygen-barrierthermoplastic resin and at least one layer interposed between saidoxygen-barrier thermoplastic resin layer and said orientingthermoplastic resin layer and being composed of a resin having anadhesiveness to both of said two resins by co-melt-extrusion; andforming the multi-layer structure into a container at a moldingtemperature satisfying the requirements represented by the followingformulae:

    |Tm -T.sub.B |≦30° C.      (8)

    T.sub.O >Tm ≧T.sub.C                                ( 9)

and

    |T.sub.B -T.sub.O |≦35° C. (1)

wherein T_(B) stands for the melting or softening point (°C.) of saidoxygen-barrier thermoplastic resin, T_(O) stands for the melting orsoftening point (°C.) of said orienting thermoplastic resin, T_(C)stands for the melting or softening point of the adhesive resin, and Tmstands for the molding temperature, and under such conditions thatorientation of the orienting thermoplastic resin is caused at least in asmallest-thickness portion of the container.
 5. A process according toclaim 4 wherein the multi-layer structure is biaxially oriented at saidmolding temperature (Tm).
 6. A process according to claim 4 wherein themulti-layer sheet is drawn into a cup at said molding temperature (Tm).